TUI: self-report lifecycle state to the herdr agent runtime

[sosidudku1]

What

When the TUI runs inside a herdr pane it now claims its own pane label through herdr's socket CLI: working while a turn is in flight, blocked while a tool approval or the plan hand-off waits on the human (with the tool name as the message), idle otherwise, and a release-agent goodbye on every exit path. Outside herdr the reporter is null and nothing changes.

Why

herdr (github.com/herdrdev/herdr, the "leave them running" agent runtime, 38k stars) labels every pane with the agent's live state. Atomic already runs fine in a pane, but shows up as an unnamed process. Self-reporting makes it a first-class agent there today, for every user, without waiting on the herdr team; it also backs our pending proposal to add built-in detection on their side (herdrdev/herdr#4201).

How

• src/tui/herdr-reporter.ts: env detection (HERDR_ENV / HERDR_BIN_PATH / HERDR_PANE_ID), a pure deriveHerdrReport over the TUI state, and a fire-and-forget reporter (spawn, stdio ignored, errors swallowed, children unref'd).
• Wired in one effect in tui-app.tsx (state observation plus unmount release) and in tui-command.ts (reporter creation, plus a release in the teardown finally for quit paths that never unmount the tree).
• Two herdr behaviors are encoded and commented, both verified against herdr 0.9.0: sequence numbers start from epoch seconds so a restart in the same pane outranks the previous run's reports, and the release must carry the next sequence number or herdr silently drops it and the label sticks to a dead pane.

Testing

• 15 unit tests in src/tui/herdr-reporter.test.ts; npx vitest run src/tui green (302 files / 3331 tests; the one unhandled error is the pre-existing llama-server EACCES flake in local-models-orchestrator-auto-update.test.ts, unrelated).
• tsc --noEmit clean.
• Live end to end against herdr 0.9.0 on macOS: pane start shows atomic · idle with no manual calls, a turn flips it to working, a file-write approval flips it to blocked, approve returns it to idle, and double ctrl+c quit leaves the herdr agent list empty.