feat: show file count per skill on dashboard skill page

[tmeschter]

Closes #2869.

What

Each skill's page in the dashboard Skills section now shows a count of the number of files in the built/output skill.

Changes

• scripts/src/dashboard/collectors/frontmatter.ts — added a countFilesRecursive helper and an addFileCounts step that populates metadata.fileCount for each skill from its directory under output/skills/. The count is recursive and includes nested sub-skill files. Applied to both the success and non-zero-exit recovery paths; collector version bumped to 1.1.0.
• dashboard/src/skills/App.tsx — added fileCount to the Skill type, read it from the health-data metadata, and render Files: N in the skill detail header.
• dashboard/src/skills/skills.css — added a matching .skills-file-count style.
• Tests — added collector tests verifying fileCount is computed recursively (including nested sub-skills) and defaults to 0 when the directory is missing.

Validation

• scripts dashboard suite: 188/188 pass (frontmatter collector: 14/14).
• dashboard skills tests: 14/14 pass.
• scripts typechecks clean; skills App compiles clean (the only tsc error is a pre-existing recharts type issue in the unrelated token-usage/App.tsx, confirmed present on the base branch).

[Copilot]

Pull request overview

Adds a “file count” metric to the Skills dashboard detail page by computing the number of files shipped in each built skill under output/skills/ and surfacing that value in the UI. This aligns with the request in #2869 to show the number of files in each skill’s built output.

Changes:

• Compute a recursive file count per built skill directory in the frontmatter dashboard collector and store it as metadata.fileCount.
• Add collector tests to verify recursive counting (including nested directories) and the missing-directory default behavior.
• Extend the Skills dashboard UI to read and render Files: N, with a matching CSS class.

Show a summary per file

File	Description
scripts/src/dashboard/collectors/frontmatter.ts	Adds recursive file counting and injects metadata.fileCount into the frontmatter category report.
scripts/src/dashboard/tests/collectors/frontmatter.test.ts	Adds coverage for recursive fileCount computation and missing-directory defaulting.
dashboard/src/skills/App.tsx	Extends Skill type and renders the file count on the skill detail header.
dashboard/src/skills/skills.css	Adds styling for the new file count line in the header.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Low