feat: search your notes — in the Library and the command palette

[praxagent]

Search your notes from TeamWork. Prax does the searching (praxagent/prax#271).

What

• In the Library: a search box at the top of the sidebar. Results show the title and a snippet; picking one opens the note.
• In the command palette (Cmd/Ctrl+K): a Notes section next to Messages, searched in parallel. Picking a note switches to the Library with it open (focusNote, like the existing focusProject).
• The relay: GET /api/library/search passes q and space to Prax, with the limit capped at 50.

Verified

• LibrarySearch.test.tsx: results show and open the note picked; nothing is searched under two characters; the palette lists notes and opens one.
• tests/test_library_search_proxy.py: the query, space and capped limit reach Prax.
• Checks: make ci green, vitest 124, tsc, eslint and the vite build clean.

[praxagent]

Rebased onto main after #90 merged. The only conflict was the import block in LibraryPanel.tsx (both sides kept). Also fixed a lint warning the rebase surfaced: CommandPalette's search effect now depends on whether notes can be opened (a boolean), not on the onOpenNote callback, so it doesn't re-search on every parent render. make ci 521, 138 frontend tests, lint back to the 19 warnings on main. Merges cleanly with #93 in either order.