Migrate the Timeline/Saved history state module to idiomatic Svelte 5
runes and wire up type-checking.
- Rename history.ts -> historyState.svelte.ts and replace the Svelte
stores with $state-backed reactive values, removing the get() calls
(the only remaining one reads the external inputStateStore). A small
localStorage-backed `persisted()` helper keeps the same keys, so user
data is preserved. Consumers read via the reactive `historyState`
getter object instead of store auto-subscriptions.
- The gist loader now replaces the in-memory revisions in one call
(setLoaderEntries) instead of appending, so loading a new gist no
longer accumulates stale revisions.
- Add svelte-check: new `check` script, a "Type check" step in the
unit-tests CI workflow, and skipLibCheck so the check passes on the
dependency .d.ts files. svelte-check reports 0 errors / 0 warnings.
- Add accessible labels to the History toggle and the per-item
Restore/Delete buttons (a11y + testability).
- Unskip tests/history.spec.ts and rewrite it against the new UI:
load-from-localStorage + restore, tab-highlight follows the mode,
save/dedupe, auto-vs-manual isolation, and delete/clear. All pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
