fix(ci): scope packed-consumer check to built packages on PRs

[EmersonBraun]

What

Scopes the "Packed consumer publication contract" check (pnpm check:packed-consumers) to the packages the PR CI actually built.

Why

On pull requests that only touch packages, the gates job builds just the affected packages and their dependents (turbo run build --filter='...[origin/main]'), but the packed-consumer check expected dist output for every package. A narrow change (for example a rag-only PR, #1829) therefore failed with missing dist for unrelated packages (angular, mcp, react-native, solid, statechart, svelte, templates, vue). PRs whose packages have many dependents passed only by coincidence.

How

When run_all=false, the check receives the set of packages that Turbo built and verifies those. When run_all=true, and in release.yml (which builds everything), it still checks all packages. The check is not weakened for any package that is actually built: a missing dist for an affected package still fails.

Reuse

This reuses Turbo's own task graph to determine which packages were built and the existing check:packed-consumers script. No new dependency.

Type of change

• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change (requires RFC reference below)
• Docs only
• Chore / internal

RFC / ADR reference

n/a (CI scope fix)

Validation

• Every acceptance criterion has contract or edge-case test evidence (pnpm test): 25 unit tests for the scoping logic.
• All applicable documented repository gates pass on this commit (all 52 quality gates plus the publication and Doc Bridge checks).
• Real simulation of a rag-only change: passes with eight unrelated dist directories absent, and fails when rag's own dist is missing.
• Changeset: not required, because no published package changes.
• Docs updated (CONTRIBUTING)
• No tests disabled or skipped to pass a gate