fix(messages): default nonmember prompt to invite - #825

* origin/main: (51 commits)
  fix(messages): default nonmember prompt to invite (#825)
  fix(toast): cancel exit-removal timers on unmount (#843)
  fix(me): share Messages sidebar working indicators and activity (#817)
  fix(messages): show typed angle-bracket text instead of dropping it (#803)
  fix(codex): default agent workspace to ~/.buzz (#831)
  View Codex and Claude sessions started in Buzz (#826)
  feat(codex): run bundled Codex with danger-full-access (#832)
  feat(codex): bundle the Codex agent type by default (#830)
  test(channels): split combined invitation paging test (#829)
  fix(dev): rebuild Vite's dependency cache on every dev start (#823)
  docs(agents): add buzz-specific test-audit skill (#797)
  fix: make inbox detail channel heading open its context (#819)
  fix(agents2): run each agent in one copy of the app (#790)
  Add Codex agents to Agents2
  fix(builderlab): complete AgentsNative mock in test (#824)
  feat(teams): edit shared team instructions in their own record (#775)
  Use Sonner for bottom-right app toasts (#813)
  Allow bounded stdin data for fixed plugin host commands (#769)
  Add native Codex agents with CLI defaults (#751)
  Register placeholder Builderlab agent type in Agents2 (#788)
  ...

Signed-off-by: morgmart <[email protected]>

## Problem

If you mention someone who isn't in the channel and press Send, Buzz
asks "Mention people outside this channel?". Since #2021 that prompt
opens with focus on **Close**. Pressing Enter again right away dismisses
it and leaves the draft unsent, so to invite you have to reach for the
mouse.

#825 had made **Invite** the default on purpose. #2021 changed it to
Close as part of a broader "focus safe controls" pass.

## Change

When you can add members, the prompt opens with focus on **Invite**
again, so Send then Enter invites the person and sends.

- Escape and Close still dismiss the prompt and keep the draft unsent.
- If you can't add members to the channel, focus still starts on Close
(no change).
- The old-agent import prompt and the archive and delete confirmations
keep #2021's safe defaults. Only this prompt changes.

## Testing

- `vitest run` (full): 1020 files and 19336 tests passed.
- Updated the `MessageComposer` tests:
- "Enter right after the prompt opens invites a nonmember and sends":
Invite has focus when the prompt opens, and Enter adds the person and
sends.
- The close/escape test now expects Invite to have initial focus and
still checks that nothing is added or sent. Its old "enter" case was the
exact behavior this PR reverses, so I removed it.
- Not yet tried in the running app.

Signed-off-by: Bradley Axen <[email protected]>
Co-authored-by: mbot <3754f8729004d95654c46dbab3129e4ab9ef05cc2534e2a3fbfc155983bd637b@buzz.block.builderlab.xyz>