Mount the Brain IdeaLoom lists view and fix its save payload

[atomantic]

Summary

Finishes the IdeaLoom lists slice that #5349 left orphaned: IdeaLoomLists shipped with no caller, so Brain > Ideas still rendered only native idea records and nothing in the running app could open the lists panel.

• Brain > Ideas now presents its two models as two sibling views — Brain ideas (federated idea records) and IdeaLoom lists (machine-local ordered lists) — with the active view addressed by ?view=lists so it is shareable, bookmarkable, and reachable from ⌘K and voice. The lists view gets its own nav-manifest entry, matching how the other query-param sub-views are registered.
• Saving a list could not work as written. The list API is strict and accepts exactly title/prompt/category/status/help/ideas, while the panel spread the whole draft record back at it, so every edit round-tripped as a 400 on the record metadata (id, schemaVersion, timestamps, importer-owned sync state). Saves now project the draft onto the schema's fields, and the required prompt/category are gated in the form with a message naming the missing field.
• Completing a list is one click that persists through the same validated save, so it can no longer silently drop unsaved edits.
• Integration state is reported honestly: an enabled integration with no vault selected, and a settings fetch that failed, each read as their own notice instead of both looking like "vault sync is disabled". None of them gate local editing.
• Both views drive the query string through the shared useUrlParams hook rather than re-rolling the merge-and-prune loop on react-router's closure-stale functional updater.

Server-side scope (#5336) is untouched; the only server change is the nav-manifest entry.

Test plan

• client/src/components/brain/tabs/IdeasTab.test.jsx (new) — the tab defaults to the native view, opens the lists view straight from the URL, records the selected view in the URL rather than local state, clears the list selection when switching back, and guards against the component being orphaned again.
• client/src/components/brain/IdeaLoomLists.test.jsx — extended to cover the exact save payload (schema keys only, no record metadata), the required-field message, one-click completion preserving unsaved edits, inline-confirm delete, the no-vault-selected notice, and an unread-settings fetch not masquerading as a disabled integration.
• cd client && npm test — 807 files / 10192 tests pass; npm run lint clean.
• cd server && npm test — 1721 files / 35366 tests pass (covers navManifest.test.js and palette.test.js).

Closes #5337