fix(lastcode): repair annotation display and editing

[lastobelus]

Thread annotations could overflow the composer banner, and choosing Edit could open a blank editor instead of the saved Markdown.

Annotations now start as a compact first-line summary with an edit timestamp. Expanding shows wrapped Markdown in the banner body, and each thread remembers its expanded or collapsed state across navigation and reloads. The editor initializes its saved text when the dialog mounts while preserving active edits and resetting canceled drafts on reopen.

Validation: 22 focused tests, web typecheck, targeted lint/formatting, and Quick CI passed for 725674d28e67e8eb4366f1f484e79756b552bbb6. Removing the editor fix makes the opening/reopening regression tests fail. Safari verification passed for opening, cancel/reopen, wrapped expanded content, expansion after reload, and collapse after navigation. Human visual acceptance passed for the editor and compact/expanded behavior. The final long-summary timestamp correction passed Safari verification: only the summary truncates, and the timestamp remains visible. Saving the edited Markdown through the dialog passed too. The first four screenshots precede this narrow correction; the final screenshot shows the current commit.

Before editing:

Populated editor:

Compact annotation:

Expanded annotation:

Long-summary timestamp on the final commit:

Generated with GPT-6 in the Codex harness, with GPT-5.6-sol regression-test assistance.