[Gap]: Document Skills management UI (currently behind SKILLS feature flag)

[danbarr]

Gap

The Skills experience at v0.30.0 — /skills (tabs: registry, installed, builds), skill detail, build detail, plus Install/Build/Uninstall/Delete-build dialogs — is currently gated behind the SKILLS feature flag in top-nav, so it's only visible after opting in at Settings → General → Experimental Features. The CLI got guides-cli/skills-management.mdx via #656 but there is no UI equivalent.

Recommended approach (mirror mcp-optimizer.mdx): add a flagged guide now with a clear "experimental, opt in via Settings" banner, OR defer until the flag flips on by default. The current state — a full feature the CLI has documented and the UI hasn't — is the gap.

Source in app (v0.30.0)

• renderer/src/routes/skills.tsx, skills_.$namespace.$skillName.tsx, skills_.builds.$tag.tsx
• renderer/src/features/skills/
• renderer/src/common/components/layout/top-nav/index.tsx:71 (feature flag gate)

Docs to update

• docs/toolhive/guides-ui/skills-management.mdx (new file) or equivalent section

Introducing PR

stacklok/toolhive-studio#1878 — feat(skills): add skills page with list, install, uninstall and build under feature flag

Parent

Part of #751.