Slack Agents support: pin QM to the top bar (agent_view)

[16francej]

Lets users pin QM to the Slack top bar (Slack Agents & AI Apps, current-generation agent_view — not the deprecated assistant tabs) and talk to it in the split pane.

What

• Manifest (src/slack/manifest.json + CLI template): features.agent_view, assistant:write scope, and the assistant_thread_started, assistant_thread_context_changed, app_context_changed events.
• New src/slack/agent-pane.ts: tracks agent threads and viewing context; guarded assistant.threads.setStatus/setTitle calls that feature-detect and self-disable on installs that haven't updated.
• Wiring (events.ts): split-pane messages are ordinary message.im thread messages, so they dispatch through the existing DM turn machinery unchanged — same sessions, same behavior. Around dispatch we set a "thinking…" status (cleared even on silent/errored turns; a posted reply clears it natively), title the thread from its first message, and pass a currently_viewing note (message app_context → saved thread context → user's last app_context_changed) into the turn's gateway context so "summarize this" works.
• Out of scope: streaming into the pane — agent-pane.ts marks the seam (setStatus is where a chat.startStream presenter slots in).

Backward compatibility

Installs whose manifest predates the feature never receive the new events, and the first missing_scope/unavailable response disables the pane API calls for the process (one warning, then silence). No turn ever hard-fails on this path. A client without assistant.* methods is a no-op.

Release notes

Slack: QM can now be pinned to the top bar (Agents & AI Apps). To enable it on an existing install, update the app manifest from src/slack/manifest.json (adds the agent_view feature, the assistant:write scope, and three assistant_*/app_context_changed events) and reinstall the app to the workspace. Requires a paid Slack plan (or a Developer Program sandbox). Installs that don't update keep working exactly as today.

Tests

test/slack-agent-pane.test.ts (13 cases): status set/cleared incl. on dispatch failure, one-time titling, context precedence and updates, no-pane and old-client no-ops, missing_scope self-disable, manifest parity test still green. Full slack suites: 366/366; tsc --noEmit and eslint clean.

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