feat: show agent conversations in the desktop inbox

[leynier]

Summary

A read-only Agent Conversations view in the desktop inbox page, next to Questions.

• A workspace filter. Each row shows the subject, participants (as "tab title (agent)" from the sidebar, falling back to the handle), the message count, the workspace, the last activity and a Group badge.
• The detail lists the messages in order (from -> to, type, time, body). It never calls markRead and has no write actions.
• conversationsChanged is registered in runtimeHostEventNames. The view refreshes on that event and on host connect and disconnect.

Stacked on the phase 2 host PR.

Validation

• New agent_conversations_view_test and conversation model tests. Line coverage of the inbox domain files is 100%.
• flutter analyze reports no issues, and the full flutter test passes (4361 passed, 4 skipped).
• The max-lines ratchet and git diff --check pass.

Risk

The list loads at most 100 conversations, and there is no participant filter in the UI yet.

[pullfrog]

Important

The reply hint pasted into an agent's terminal cannot be run, and the status filter only searches the newest page of threads.

Reviewed changes — the full stack on main, not only the Agent Conversations view in the title: persisted ext: questions, the desktop and mobile inbox, the CLI, and a read-only conversation list.

• Inbox store. Questions and replies live in orchestrationMessages, with expiry, a pending cap, retention, and additive inboxV1. The host protocol version is not bumped.
• Desktop inbox. A shell overlay beside Run Board and Automations. Ask, follow-up, cancel, and purge. Opening a question marks it read for every client. Notifications omit reply text.
• Agent conversations. A second view lists what agents send each other and never calls markRead.
• Phone and CLI. Paired phones can ask and read, but not inbox.wait. alera inbox and orchestration ask --no-wait use the same host verbs.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using grok-4.7 ｜ 𝕏}

[pullfrog]

Important

The reply hint pasted into an agent terminal still cannot be run. This commit does not change that banner.

Reviewed changes — the rewritten desktop conversations commit since 43b0989, now based on feat/agent-conversations.

• Questions after an ask. Selecting a thread, composing, or opening a reply notification shows Questions, so a question sent from Agent Conversations is visible.
• Paged conversations. Load More continues from nextBefore and drops extra pages when the watched first page refreshes.
• Coverage. Widget and navigation tests lock the view switch and the page request.

⚠️ Reply hint cannot be run

The external banner still tells the agent to run alera orchestration reply --id <id> --body-stdin <<'EOF' ... EOF. That form fails in PowerShell 5.1, cmd, and nushell, and a one-line heredoc does not close in bash, so --body-stdin waits for an EOF the PTY never sends. Agents that follow it fail or hang instead of answering.

Technical details

# Portable inbox reply hint

## Affected sites
- `rust/alera-cli/src/terminal_host/orchestration/message_formatter.rs:60` — external banner prescribes `--body-stdin <<'EOF' ... EOF`
- `rust/alera-cli/src/terminal_host/orchestration/message_formatter.rs:249` — the unit test locks that string in

## Required outcome
- The banner must name a reply command the user's interactive shell can run (PowerShell 5.1, cmd, nushell, and bash) without waiting for an EOF the PTY will not send.
- Non-inbox banners already use `--body`. Do not prescribe a bash heredoc or bare `--body-stdin`.

## Open questions for the human
- This file is on the base, not in this commit. Land the fix on `feat/agent-conversations` or here.

  ^{｜ Fix it ➔ ｜ View workflow run ｜ Using grok-4.7 ｜ 𝕏}