Stop tracking generated app-shell skills

[IzumiSy]

Motivation

packages/core/skills is generated output, but the source of truth lives under catalogue/.

Keeping the generated tree checked into git made normal changes noisy and easy to get wrong: catalogue edits and generated output were mixed together, generated files could drift from their source, and it was too easy to treat generated files as something to edit directly instead of regenerating from the catalogue inputs.

This PR keeps the generated skills out of git, keeps the generator output in sync with the catalogue inputs, and moves validation to the catalogue side without making packages/core depend on catalogue paths.

Design Decision

Instead of treating generated skills as tracked source files, this change treats them as build output.

The release flow stays on the existing root pnpm build path, where catalogue already owns skill generation. This keeps packages/core free of any direct dependency on catalogue paths or package-local generation hooks.

To keep a guardrail in place, the catalogue now carries a small manifest-based check. The test compares the generated packages/core/skills/** file set against catalogue/expected-skills-files.txt, and Turbo is configured to run local build before test so the generated tree exists before validation runs.

The generator was also made deterministic by sorting discovered inputs and normalizing the generated index tables, so catalogue changes produce stable skill output instead of order-dependent churn.

Summary

• stop tracking packages/core/skills in git and ignore regenerated local output
• keep skill generation owned by catalogue / root build flow, without adding a packages/core-local generation hook
• add a catalogue-side generated-skills manifest check and wire Turbo test to depend on local build output
• make generated skill output deterministic and refresh the catalogue-driven skill content and template metadata

[IzumiSy]

The latest CI error is totally not related to changes in this PR and I cannot reproduce it locally, so I guess it's ok to ignore it only at this time. fixed via #376 (comment)

[IzumiSy]

Note: 1cabdb9e is intentionally out of scope for the main focus of this PR.

CI started failing after the turbo.json change that added build to the test.dependsOn chain, which appears to have shifted task timing/scheduling in CI and surfaced a pre-existing flaky snapshot rather than introducing a functional regression. The root cause was Base UI briefly appending an invisible U+2060 marker to the live-region text in the combobox / autocomplete snapshots.

The commit stabilizes those tests by waiting for the live region to settle before snapshotting.