feat(skills): add a Skills page under Settings → Build

[rafavalls]

What is this contribution about?

Describe your changes and why they're needed.

Skills already drive agent behaviour at runtime (buildSkillCatalog → <available-skills>), but the only way to see or add one was to browse raw folders in the Library. This adds Settings → Build → Skills: a page listing the org's whole catalog (its own, built-in public sets, synced repos) with search and origin filter chips, plus folder-import for new ones. Skills are SKILL.md folders on org-fs, so import is the Library's upload with the format enforced — pick a folder containing a SKILL.md and its files land under home/skills/<slug>/ with subdirectories intact (files are grouped by destination dir; flattening would collapse references/style.md onto the root). Cards reuse the Library's FolderIcon so a skill looks like the same object on both pages: Finder blue for the org's own (deletable), graphite plus a view-only badge for read-only sets and repos, with the body glyph naming the origin. Filter chips are derived from the catalog rather than hardcoded, since which public sets exist is deployment config (ORGFS_PUBLIC_SETS) and repo volumes are per-org.

Web-only — no API, schema, endpoint or migration changes. Everything composes existing org-fs routes (/fs/skills, PUT/DELETE file, list).

How did you verify your code works?

Name the tests you ran or added and what you observed. "Verified manually" or "existing tests" without specifics doesn't count.

• tsc --noEmit (apps/web) and oxlint clean on all touched files; knip reports no orphans.
• bun run --cwd=apps/web test: 2987 pass / 112 fail. I re-ran with this branch's changes stashed and got byte-identical counts (2987/112/13 errors), so the failures pre-date this branch and none are introduced here.
• react.d.ts (the webkitdirectory augmentation) is load-bearing, not decorative: removing the file reproduces exactly 2 webkitdirectory type errors, so the attribute is genuinely type-checked rather than silently any. It lives in its own module file because putting declare module "react" in the script-scoped globals.d.ts declares an ambient module that shadows React entirely (~30 errors across packages/ui).
• Seeded a real multi-file skill (home/skills/weekly-report with references/{template,tone}.md) into a local org through OrgFs.write() and confirmed both consumers agree: the route's filesExist probe returns hasSkill=true (so the Library renders a skill card), and detectSkills returns id=home/skills/weekly-report with the parsed name/description (so agents get it in <available-skills>).

Screenshots/Demonstration

Add screenshots or a Loom video if your changes affect the UI.

Page layout follows the Connections page rhythm (title → search → chips → cards on one gap-6 column); cards follow ProjectCard.

How to Test

Provide step-by-step instructions for reviewers to test your changes:

1. Go to Settings → Build → Skills. The built-in core / storefront sets should list as graphite folders with a view-only badge; filter chips show one per origin with counts.
2. Click a card — the Library's skill preview opens (SKILL.md rendered, bundled files in the sidebar).
3. Click Import skill and pick a folder containing a SKILL.md (nested subfolders are fine). It appears as a blue folder attributed to your org, with a delete action in its hover menu.
4. Pick a folder without a SKILL.md — expect a toast telling you to pick the skill's own folder, and no upload.
5. Confirm the imported skill also shows in Library and is offered to agents via the chat / picker.

Migration Notes

If this PR requires database migrations, configuration changes, or other setup steps, document them here. Remove this section if not applicable.

None.

Review Checklist

• PR title is clear and descriptive
• Changes are tested and working
• Documentation is updated (if needed)
• No breaking changes

🤖 Generated with Claude Code

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Summary by cubic

Adds Settings → Build → Skills so orgs can see every skill available to their agents (own, built-in sets, synced repos) and import new ones, instead of browsing raw folders in the Library.

• Lists the full org skill catalog with search and origin filter chips; clicking a card opens the Library's skill preview.
• Importing a folder with a SKILL.md at its root uploads it under home/skills/<slug>/ with subdirectories intact; other folders are rejected with an error toast.
• Imports refuse existing slugs, drop dotfiles and tooling dirs, cap at 200 files, and roll back a partially failed upload.
• Failed catalog loads render their own error state, not an empty state.
• Cards reuse the Library's FolderIcon: blue for the org's own deletable skills, graphite with a view-only badge for read-only sets and repos.
• Web-only; no API, schema, or migration changes. Adds en and pt-br translations.

^{Written for commit cc6aec8. Summary will update on new commits.}