This reverts commit 787ed46.

…chain integration, force-refresh) (#12153)

Port pnpm's custom resolver hooks to the Rust pacquet engine: a pnpmfile can export a top-level `resolvers` array whose entries override built-in dependency resolution and force re-resolution when needed. See #10389 for the TypeScript-side feature request that motivated this port.

## What's included

- **Hook contract** — `CustomResolver` trait (`canResolve` / `resolve` / `shouldRefreshResolution`) mirroring `hooks/types/src/index.ts`. All three methods are optional upstream, so the Node worker reports per-resolver capability flags in one IPC round trip and pacquet skips calls a resolver doesn't implement (mirrors pnpm's `if (!customResolver.canResolve || !customResolver.resolve) continue` and `checkCustomResolverForceResolve`'s hook filter).
- **Node IPC** — the long-lived pnpmfile worker gained `resolvers` (capabilities) and `resolver` (method invocation) requests. Methods are invoked with `this` bound to the resolver object, like pnpm. Pending-request cleanup is cancellation-safe via an RAII guard.
- **Adapter & chain integration** — `CustomResolverAdapter` bridges the JSON hook contract to the typed `Resolver` trait. Custom resolvers are built into the inner resolver chain ahead of the built-ins (upstream chain priority), inside the prefetching/observing wrappers so their tarball results get resolve-time prefetch and pnpr streaming. `canResolve` results are memoized keyed `alias@bareSpecifier`, exactly like pnpm's `getCustomResolverCacheKey`. A resolver-returned `manifest` passes through (pnpm spreads the whole hook result). Payloads match upstream: `prevSpecifier`, and resolve opts carry `lockfileDir` / `projectDir` / `preferredVersions` / `currentPkg`.
- **`shouldRefreshResolution` semantics** — port of `checkCustomResolverForceResolve`: the hook receives the merged packages+snapshots entry (pnpm's in-memory `PackageSnapshot`), checks run concurrently with first-true/first-error short-circuit, and a throwing hook aborts the install (`PNPMFILE_FAIL`). A `true` verdict defeats both up-to-date optimizations, as documented in the hook's contract:
  - the prefer-frozen dispatch consults the hook (pnpm: `forceResolutionFromHook` → `needsFullResolution` blocks `isFrozenInstallPossible`) and routes to the fresh-resolve path with lockfile reuse disabled (`UpdateReuseScope::None`);
  - the optimistic repeat-install fast path now ports the pnpmfile branch of `patchesOrHooksAreModified`: the workspace state records the loaded pnpmfile list, and an added/removed/edited pnpmfile invalidates the mtime check.
- **`CurrentPkg`** — added to `ResolveOptions`, matching upstream's `currentPkg` shape `{id, name?, version?, resolution, publishedAt?}` (camelCase).

## Tests

- Adapter unit tests: missing `id`/`resolution`, invalid shapes, `canResolve` memoization, payload shapes, manifest passthrough.
- `check_custom_resolver_force_resolve` unit tests: port of upstream's `checkCustomResolverForceResolve.ts` suite (capability filter, true/false/error propagation, merged snapshot payload).
- Node IPC integration tests against a real pnpmfile: capabilities, `this` binding, round trips, error propagation, cancellation cleanup.
- CLI e2e tests against the mock registry: custom resolver precedence over the npm resolver, `shouldRefreshResolution` re-resolving past an up-to-date lockfile, and a throwing hook failing the install.