* feat: edit/revert sent messages via server revert API
Wires the mobile client up to the opencode server's session.revert /
session.unrevert endpoints (the same primitive the desktop TUI uses to
edit the last message). Long-press a user message bubble -> "Edit
message" reverts it server-side and prefills the composer with its
text; a banner offers Undo while the revert is pending (it's only
cleaned up server-side on the next prompt). Degrades gracefully with
an alert on older servers that 404 the /revert route.
Closes#56
* fix(revert): address code review findings on edit/revert message flow
- Confirm before overwriting an in-progress composer draft when editing
a sent message (F2)
- Restore reverted message's file attachments into the composer, not
just its text (F3)
- Distinguish 401/403 from other revert failures with an accurate
"Authentication failed" message instead of a generic one (F4)
- Exclude optimistic "temp-" message IDs from the revert cutoff
comparison so concurrently-sent messages aren't hidden (F9)
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Co-authored-by: engineer <engineer@gray-knight-m1.local>