[BUG] commit 163cdfd31 breaks interpolation in extended files

### Description

Current behavior is the following error, with a stacktrace (included in reproduction steps):

```
panic: interface conversion: interface {} is string, not map[string]interface {}
```

I also get a different error if I remove a mount option next to the interpolation. Both configs and errors included in reproduction steps.

Expected containers to come up when I did `docker compose up`. Error(s) also happens with `docker compose config`, and it's got something to do with combining interpolation and extended files.

It seems the bug was introduced in 163cdfd31, which adds a test and updates the `compose-go` dependency.

Checking out `compose-go`, with `compose` set to `163cdfd31~`, it seems the bug was introduced there in compose-spec/compose-go@65600ce.

Adding report here rather than there because I'm observing and replicating the error from `compose`.

### Steps To Reproduce

Script to reproduce:

```bash
d=/tmp/docker-compose-interpolation-test-extended-with-ro

set -e
mkdir "$d"
cd "$d"

cat > docker-compose.yml <<EOF
services:
  foo:
    extends: { file: foo.yml, service: foo }
EOF

cat > foo.yml <<EOF
services:
  foo:
    image: bash
    volumes:
      - \${FOO:-/dev/null}:/tmp/foo:ro
EOF

docker compose config
```

Result:

```
panic: interface conversion: interface {} is string, not map[string]interface {}

goroutine 1 [running]:
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).absVolumeMount(0x2?, {0x5ea29c98d9c0?, 0xc0007137a0?})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:123 +0x1be
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).resolveRelativePaths(0xc00047e6c0, {0x5ea29c98d9c0, 0xc0007137a0}, {0xc00041f770, 0x17})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:74 +0xf0
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).resolveRelativePaths(0xc00047e6c0, {0x5ea29c959c80, 0xc00073aa98}, {0xc00041f758, 0x14})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:88 +0x339
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).resolveRelativePaths(0xc00047e6c0, {0x5ea29caa51c0, 0xc00035d590}, {0xc000723da0, 0xc})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:80 +0x22e
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).resolveRelativePaths(0xc00047e6c0, {0x5ea29caa51c0, 0xc00035d560}, {0xc000723c98, 0x8})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:80 +0x22e
github.com/compose-spec/compose-go/v2/paths.(*relativePathsResolver).resolveRelativePaths(0xc00047e6c0, {0x5ea29caa51c0, 0xc00035d380}, {0x0, 0x0})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:80 +0x22e
github.com/compose-spec/compose-go/v2/paths.ResolveRelativePaths(0xc00035d380, {0x5ea29c81ad28, 0x1}, {0xc0007137c0, 0x2, 0x2})
    github.com/compose-spec/compose-go/v2@v2.1.4/paths/resolve.go:50 +0x827
github.com/compose-spec/compose-go/v2/loader.getExtendsBaseFromFile({0x5ea29ce88128, 0xc00035c810}, {0xc000723bd8, 0x3}, {0xc000723c78, 0x3}, {0xc000781c80, 0x3e}, {0xc000723c50, 0x9}, ...)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/extends.go:203 +0x985
github.com/compose-spec/compose-go/v2/loader.applyServiceExtends({0x5ea29ce88128, 0xc00035c810}, {0xc000723bd8, 0x3}, 0xc00035c9c0, 0xc00054fcb0, 0xc0005a0c20, {0xc0005a0900, 0x1, 0x1})
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/extends.go:101 +0x4da
github.com/compose-spec/compose-go/v2/loader.ApplyExtends({0x5ea29ce88128, 0xc00035c810}, 0xc00035c990, 0xc00054fcb0, 0xc0005a0c20, {0xc0005a0900, 0x1, 0x1})
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/extends.go:43 +0x174
github.com/compose-spec/compose-go/v2/loader.loadYamlFile.func1({0x5ea29caa51c0?, 0xc00035c990?}, {0xc0005a0900, 0x1, 0x1})
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:438 +0x11d
github.com/compose-spec/compose-go/v2/loader.loadYamlFile({0x5ea29ce88160, 0xc0003eec30}, {{0xc000781c80, 0x3e}, {0xc000536200, 0x40, 0x200}, 0x0}, 0xc00054fcb0, {0xc000781c80, ...}, ...)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:490 +0x564
github.com/compose-spec/compose-go/v2/loader.loadYamlModel({0x5ea29ce88160, 0xc0003eec30}, {{0x0, 0x0}, {0xc000781c80, 0x2b}, {0xc00035c0f0, 0x1, 0x1}, 0xc00057dd70}, ...)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:364 +0x1a5
github.com/compose-spec/compose-go/v2/loader.load({0x5ea29ce88160, 0xc0003eec30}, {{0x0, 0x0}, {0xc000781c80, 0x2b}, {0xc00035c0f0, 0x1, 0x1}, 0xc00057dd70}, ...)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:512 +0x38b
github.com/compose-spec/compose-go/v2/loader.loadModelWithContext({0x5ea29ce88160, 0xc0003eec30}, 0xc00069eb40, 0xc00054fcb0)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:336 +0x105
github.com/compose-spec/compose-go/v2/loader.LoadWithContext({0x5ea29ce88160, 0xc0003eec30}, {{0x0, 0x0}, {0xc000781c80, 0x2b}, {0xc00035c0f0, 0x1, 0x1}, 0xc00057dd70}, ...)
    github.com/compose-spec/compose-go/v2@v2.1.4/loader/loader.go:312 +0xd8
github.com/compose-spec/compose-go/v2/cli.(*ProjectOptions).LoadProject(0xc00054fc20, {0x5ea29ce88160, 0xc0003eec30})
    github.com/compose-spec/compose-go/v2@v2.1.4/cli/options.go:445 +0x128
github.com/docker/compose/v2/cmd/compose.(*ProjectOptions).ToProject(0xc000315720, {0x5ea29ce88160, 0xc0003eec30}, {0x5ea29ce9f160, 0xc000420c80}, {0x5ea29e0fd3a0, 0x0, 0x0}, {0xc00057dce0, 0x6, ...})
    github.com/docker/compose/v2/cmd/compose/compose.go:318 +0x539
github.com/docker/compose/v2/cmd/compose.(*configOptions).ToProject(0xc0005a16d0, {0x5ea29ce88160, 0xc0003eec30}, {0x5ea29ce9f160, 0xc000420c80}, {0x5ea29e0fd3a0, 0x0, 0x0}, {0x0, 0x0, ...})
    github.com/docker/compose/v2/cmd/compose/config.go:62 +0x16a
github.com/docker/compose/v2/cmd/compose.runConfigInterpolate({0x5ea29ce88160, 0xc0003eec30}, {0x5ea29ce9f160, 0xc000420c80}, {0xc000315720, {0x5ea29c4a6c07, 0x4}, {0x0, 0x0}, 0x0, ...}, ...)
    github.com/docker/compose/v2/cmd/compose/config.go:181 +0x72
github.com/docker/compose/v2/cmd/compose.runConfig({0x5ea29ce88160?, 0xc0003eec30?}, {0x5ea29ce9f160, 0xc000420c80}, {0xc000315720, {0x5ea29c4a6c07, 0x4}, {0x0, 0x0}, 0x0, ...}, ...)
    github.com/docker/compose/v2/cmd/compose/config.go:159 +0xc5
github.com/docker/compose/v2/cmd/compose.configCommand.func2({0x5ea29ce88160?, 0xc0003eec30?}, {0x5ea29e0fd3a0?, 0xc0000061c0?, 0x5ea29c47933c?})
    github.com/docker/compose/v2/cmd/compose/config.go:126 +0x105
github.com/docker/compose/v2/cmd/compose.configCommand.Adapt.func4({0x5ea29ce88160?, 0xc0003eec30?}, 0x2?, {0x5ea29e0fd3a0?, 0x5ea29ce6d260?, 0x78b32a?})
    github.com/docker/compose/v2/cmd/compose/compose.go:125 +0x30
github.com/docker/compose/v2/cmd/compose.configCommand.Adapt.AdaptCmd.func7(0xc0001f6f08, {0x5ea29e0fd3a0, 0x0, 0x0})
    github.com/docker/compose/v2/cmd/compose/compose.go:101 +0x154
github.com/docker/cli/cli-plugins/plugin.RunPlugin.func1.1.2(0xc0001f6f08, {0x5ea29e0fd3a0, 0x0, 0x0})
    github.com/docker/cli@v27.0.3+incompatible/cli-plugins/plugin/plugin.go:64 +0x6c
github.com/docker/compose/v2/cmd/cmdtrace.Setup.wrapRunE.func2(0xc0001f6f08?, {0x5ea29e0fd3a0?, 0x0?, 0x0?})
    github.com/docker/compose/v2/cmd/cmdtrace/cmd_span.go:85 +0x63
github.com/spf13/cobra.(*Command).execute(0xc0001f6f08, {0xc00014baf0, 0x0, 0x0})
    github.com/spf13/cobra@v1.8.1/command.go:985 +0xaca
github.com/spf13/cobra.(*Command).ExecuteC(0xc000020308)
    github.com/spf13/cobra@v1.8.1/command.go:1117 +0x3ff
github.com/spf13/cobra.(*Command).Execute(...)
    github.com/spf13/cobra@v1.8.1/command.go:1041
github.com/docker/cli/cli-plugins/plugin.RunPlugin(0xc000420c80, 0xc000440908, {{0x5ea29c4a7737, 0x5}, {0x5ea29c4b1636, 0xb}, {0x5ea29c82072c, 0x6}, {0x0, 0x0}, ...})
    github.com/docker/cli@v27.0.3+incompatible/cli-plugins/plugin/plugin.go:79 +0x145
github.com/docker/cli/cli-plugins/plugin.Run(0x5ea29ce58b18, {{0x5ea29c4a7737, 0x5}, {0x5ea29c4b1636, 0xb}, {0x5ea29c82072c, 0x6}, {0x0, 0x0}, {0x0, ...}})
    github.com/docker/cli@v27.0.3+incompatible/cli-plugins/plugin/plugin.go:94 +0x165
main.pluginMain()
    github.com/docker/compose/v2/cmd/main.go:38 +0xa5
main.main()
    github.com/docker/compose/v2/cmd/main.go:98 +0x19c
```

Removing `:ro` (the readonly mount option):

```bash
d=/tmp/docker-compose-interpolation-test-extended-without-ro

set -e
mkdir "$d"
cd "$d"

cat > docker-compose.yml <<EOF
services:
  foo:
    extends: { file: foo.yml, service: foo }
EOF

cat > foo.yml <<EOF
services:
  foo:
    image: bash
    volumes:
      - \${FOO:-/dev/null}:/tmp/foo
EOF

docker compose config
```

Result:

```
invalid interpolation format for services.foo.volumes.[].source.
You may need to escape any $ with another $.
${FOO
```

And here's a successful interpolation if I don't extend and use a single yml:

```bash
d=/tmp/docker-compose-interpolation-test-not-extended-with-ro

set -e
mkdir "$d"
cd "$d"

cat > docker-compose.yml <<EOF
services:
  foo:
    image: bash
    volumes:
      - \${FOO:-/dev/null}:/tmp/foo:ro
EOF

docker compose config
```

Result:

```
name: docker-compose-interpolation-test-not-extended-with-ro
services:
  foo:
    image: bash
    networks:
      default: null
    volumes:
      - type: bind
        source: /dev/null
        target: /tmp/foo
        read_only: true
        bind:
          create_host_path: true
networks:
  default:
    name: docker-compose-interpolation-test-not-extended-with-ro_default
```

### Compose Version

```Text
$ docker compose version
Docker Compose version 2.29.0
$ docker-compose version
Docker Compose version 2.29.0
```



### Docker Environment

```Text
Client:
 Version:    27.0.3
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  0.15.1
    Path:     /usr/lib/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  2.29.0
    Path:     /usr/lib/docker/cli-plugins/docker-compose

Server:
 Containers: 271
  Running: 1
  Paused: 0
  Stopped: 270
 Images: 284
 Server Version: 27.0.3
 Storage Driver: overlay2
  Backing Filesystem: btrfs
  Supports d_type: true
  Using metacopy: true
  Native Overlay Diff: false
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ae71819c4f5e67bb4d5ae76a6b735f29cc25774e.m
 runc version: 
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.9.6-arch1-1
 Operating System: Arch Linux
 OSType: linux
 Architecture: x86_64
 CPUs: 32
 Total Memory: 125.7GiB
 ID: TVST:4T34:N6W7:FSIT:7HOI:IDG3:NUS4:A4AA:SUGG:WO3F:WZPJ:Y73Y
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Live Restore Enabled: false
```


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[BUG] commit 163cdfd31 breaks interpolation in extended files #11994

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[BUG] commit 163cdfd31 breaks interpolation in extended files #11994

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