Settings v2: simple/advanced view, changed markers and reset

[raiseCatError]

Implements #169 (see Deferred).

Stacked on #223 (feature/168-authored-markdown). Merge order: #203, #217, #218, #219, #220, #221, #222, #223, then this PR.

What changed (Config view of /settings)

• Simple and advanced view: rows can be marked advanced. Config lists simple rows by default, A shows or hides advanced rows, and searching always covers every row. Marked advanced: divider density, history colors, syntax colors, output folding, multiple detached sessions and empty-prompt prediction.
• Changed-from-default: a changed value gets a text marker (•, or * in safe glyph mode), so it does not rely on color.
• Reset current setting: R resets only the focused inline setting to its shipped default, and the footer names the default (R reset to Daily). It is not offered on unchanged rows and does nothing while typing in search. No confirmation, since it is one setting and undo is not required.
• Remembered position, search and advanced toggle survive closing and reopening within one run. They are not persisted, so there is no config change.
• The command palette's config targets reveal an advanced row if needed and clear a stale search.
• Search, categories/tabs and the existing safe-write config path are unchanged. The Tool configuration center: read/edit supported tool config inside /settings #83 architecture is untouched.

Compatibility

No config schema change, no migration, and existing values are untouched. Existing tests that assumed the full flat list now opt into the advanced view; the intended change is that advanced rows are hidden by default.

Deferred

• Live preview beyond the existing Layout panel preview.
• Using the shared form controls (multi-select, confirmation) here; the reset stays a single keypress.
• Advanced rows for surfaces, gradients and motion, which have no user-facing settings yet.
• Rendering the footer from the shared action model; it keeps its established phrasing.

Verification

tests/settingsV2.test.ts; full suite 673/673, typecheck, build and git diff --check clean.