Polish Threadboard and fix task refresh and ownership edge cases

[vrnrn]

Threadboard could reopen a closed task after a delayed read, combine pages from different board revisions, and lose a launch reservation on a same-column move. This pass fixes those cases, hardens launch binding and installer cleanup, and prepares preview 0.1.4-dev.8.

The website, README, sample tasks, and installation docs now describe the product more directly. The site uses a quieter palette, more readable mobile text, refreshed screenshots and social artwork, and less CSS. Its interactive demo follows the app's ownership and launch rules, and website CI rebuilds the plugin before packaging the download.

Additional changes:

• Preserve filters on archive navigation and recover from failed reads; keep loaded pages on refresh; discard stale task responses; improve keyboard/modal behavior.
• Select the newest submission even when run timestamps match, recheck prerequisites before binding a launch, and skip unchanged project updates.
• Type-check the website demo, detect stale committed bundles in CI, and cancel superseded checks. Collect each dependency license once on case-sensitive and case-insensitive filesystems; leave runtime-dependent gzip counts out of byte-for-byte comparison.

Validation: type checking; 30 backend/installer tests; 27 app UI tests; 8 website tests including accessibility in both themes at 320–1440px; four screenshot fixtures; release audit; checksummed packaging; isolated installation/reinstallation with saved data; dependency audits. Existing storage, startup, concurrency, populated-runtime, live-update, and browser-rendering performance budgets pass. The 200-card browser fixture measured 294 ms p95 at 4× CPU throttling on the development machine.

Linux CI passes for the final commit on Node 22.13 and 24, including all performance, release, and installation checks. Website CI also passes.

The protected planning documents are unchanged. This PR does not deploy the website, publish a release, or update the installed plugin. Native Codex desktop behavior and Windows installation retain their existing manual verification gaps.