feat(sidebar): persist user-pinned custom project paths in localStorage

[3bluebytes]

Problem

The directory picker's "Custom path" branch validates a path server-side but only stores the choice in component state. The path vanishes on reload and is absent from the project selector, so users have to re-pick the same directory every time they open Pi Web.

Project list (getRecentProjects) is computed purely from session files on disk, so any path the user has only ever browsed (no session started) never appears in the selector.

Fix

Pin successfully-validated custom paths in window.localStorage["pi-web:custom-project-paths"] and merge them into getRecentProjects. Session-derived projects still win on overlap because they are canonicalised against the server's filesystem view.

• New lib/custom-projects.ts with loadCustomProjects / saveCustomProject / removeCustomProject helpers. Falls back gracefully when storage is unavailable (privacy mode, SSR, denied access).
• getRecentProjects now accepts an optional customProjects list and exposes isCustomOnlyProject so the sidebar can show a remove button only for entries not backed by any session.
• The sidebar calls saveCustomProject after a successful /api/cwd/validate and refreshes state from storage. A small × button removes a pinned entry on hover.
• i18n: new sidebar.removeCustomProject key in en + zh-CN.

Tests

• New lib/custom-projects.test.mjs covers round-trip, dedup-by-key, malformed entries, removal, and storage-unavailable / SSR fallback.
• New cases in lib/project-groups.test.mjs cover the merge logic and isCustomOnlyProject.
• Full suite (npm test): 597/597 pass.
• npm run lint: clean.
• npm run build: clean (no new warnings).

Screenshots

Will attach after first reply.

[agegr]

I don’t think this is necessary. The project list should only include directories with existing sessions; custom paths can remain temporary until a session is created.

[agegr]

A simpler alternative would be to remember the last successfully selected cwd and prefill the custom picker with it. This avoids adding directories without sessions to the project list.

a5630c1