[flankero-dev]

Storage errors could appear saved, a damaged saved copy could be overwritten, and failed snapshot refreshes left stale data actionable. This PR adds explicit persistence/recovery feedback, pre-write version checks, snapshot diffs and confirmations, strict date/Unicode validation, bounded history and draft preservation. It also fixes Windows static assets, path/symlink containment, malformed UTF-8, invalid SQLite state and WebKit long-assignee overflow.

Verification completed on head 90765909eaf98d8ea1784c5b6666d7e32dc1e787:

• Final CI: all four jobs pass — Chromium on Linux/Windows, Firefox and WebKit on Linux, Node 24.
• 71 unit tests; format, lint, build, existing browser suites, 18 audit scenarios and four axe states pass. CI artifacts contain screenshots and JSON.
• 30,000 history entries: local median dialog latency 4,061 → 216 ms, or 20,692 → 596 ms with 4× CPU emulation (seven samples; exploratory). Full history remains exportable.
• All S01–S21 dispositions and reproduction commands: audit notes. The owner's handoff contains the combined 49-entry register, before failures, synthetic fixtures, performance series and final CI evidence.

Limits: localStorage cannot provide atomic cross-process CAS; SQLite snapshots retain transactional ETags. Real screen readers, physical mobile devices and native browser zoom remain unverified; CSS zoom/axe are not WCAG certification. Firefox/WebKit clipboard checks use an explicitly labelled double. Public-demo smoke covers the existing baseline only.

Compatibility: no SQLite schema/version migration. Historically accepted ambiguous dates/unsafe identifiers now fail validation with raw recovery rather than guessed migration. Back up JSON and SQLite before upgrade/rollback; older code restores weaker guards. See decisions.

Ready for owner review; kept as a draft. No merge or production deployment has been performed or authorized. Merge may start the existing deployment workflow.