Phase 2.1 of the AppProcess migration, stacked on #27178.

Summary

Replaces the spawn-and-collect dance in src/installation/index.ts with AppProcess.run. The service now yields AppProcess.Service instead of ChildProcessSpawner.ChildProcessSpawner, and defaultLayer provides AppProcess.defaultLayer (which provides CrossSpawnSpawner underneath).

Call sites migrated

packages/opencode/src/installation/index.ts:

• text(cmd, opts) (was lines 96-110): spawn -> collect stdout via Stream.mkString -> await exit code -> catch -> "". Now: single appProcess.run(ChildProcess.make(...), { interpretExitCode: acceptAnyExit }) then .stdout.toString("utf8").
• run(cmd, opts) (was lines 112-129): spawn -> collect stdout+stderr concurrently -> exit code -> catch -> default failure. Now: single appProcess.run with acceptAnyExit so caller can inspect .exitCode itself (preserves prior behavior where non-zero exits were not failures).
• upgradeCurl(target) (was lines 139-159): spawn bash with piped stdin, collect, exit. Now: appProcess.run(ChildProcess.make("bash", [], { stdin: Stream.make(bodyBytes), ... }), { interpretExitCode: acceptAnyExit }).

Layer dependency change:

• Old: Layer.Layer<Service, never, HttpClient.HttpClient | ChildProcessSpawner.ChildProcessSpawner>
• New: Layer.Layer<Service, never, HttpClient.HttpClient | AppProcess.Service>
• defaultLayer: dropped direct CrossSpawnSpawner.defaultLayer (now provided via AppProcess.defaultLayer).

Behavior preservation

All three helpers needed interpretExitCode: () => "success" (aliased acceptAnyExit). The pre-existing helpers ignored the exit code on purpose:

• text is used in method() to probe package managers that may not be installed (e.g., npm list -g on a system without npm). Non-zero exit must not throw.
• run returns { code, stdout, stderr }, and callers explicitly check code !== 0 (e.g., tap.code !== 0, pull.code !== 0). Letting AppProcess fail on non-zero would lose stdout/stderr from the caller's check.
• upgradeCurl shares the run-style return shape; the existing Effect.orDie only covers spawn failures, not non-zero exits.

So I used acceptAnyExit rather than custom catch translation. The Effect.catch(() => "") / Effect.catch(() => { code: 1, ... }) wrappers are kept to handle spawn-time failures (AppProcessError), matching prior semantics.

Test updates: test/installation/installation.test.ts composes AppProcess.layer over the existing mockSpawner (which provides ChildProcessSpawner) so the mock spawner still drives the test. All 9 existing tests pass.

LOC delta

packages/opencode/src/installation/index.ts: -1 line (211 insertions, 212 deletions).

Verification

• bun run typecheck (clean)
• bun run test test/installation/installation.test.ts -> 9 pass

Test plan

• Typecheck passes
• Existing installation tests pass