Integrate reviewed contributions #195–#211

[hamzamerzic]

Summary

Integrates the reviewed contribution set from #195 through #211 as one coherent, up-to-date change so the overlapping shell, chat, onboarding, CI, and deployment improvements can be validated and landed together.

All original contribution commits and authorship are preserved. The integration review resolved three overlaps:

• keeps one shared pane-entry animation clock from fix(shell): coordinate pane entry as one beat #199 rather than retaining the superseded proportional timing path from fix(shell): preserve pane velocity at split extremes #191;
• combines attachment-only messages, composer history, and native textarea sizing in the single composer path;
• keeps question cards at their frozen reading position when Android viewport growth would otherwise make that position unreachable, while stripping the temporary reservation before persistence;
• reconciles recovered chats after a missed reconnect event, scopes large tool-output lookups to the visible detail page, and clears browser-restored composer geometry from authoritative empty drafts.

Included contributions

#195, #196, #197, #198, #199, #200, #201, #202, #203, #204, #205, #206, #207, #208, #209, #210, and #211.

Review and validation

• verified every listed PR head is an ancestor of this branch;
• reviewed the complete combined source diff and merge boundaries;
• checked for private/runtime paths, conflict markers, direct chat JSON writes, generated artifacts, and whitespace errors;
• frontend unit: 1,863 passed;
• frontend hooks: 47 passed;
• production frontend build passed;
• backend local run: 2,996 passed and 1 skipped; five environment-coupled assertions encountered the live instance's checkout/build stamps and root-owned boot sentinel, which the isolated hosted run does not share;
• hosted privacy, backend, frontend, and browser checks are the merge gate.

[hamzamerzic]

Additional review fixes now included in the integration head:

• reconcile recovered chat tombstones after event-stream reconnect, matching the app-identity path;
• scope historical tool-sidecar lookup to the candidate IDs on the requested page;
• clear stale native textarea geometry when an empty composer returns from background or bfcache.

Fresh local validation on the combined head: 1,863 frontend tests passed, 47 hook tests passed, and the production frontend build passed. Hosted checks on head 39eaf7e remain the merge gate.