fix(tmux,run,hooks): the four pre-existing bugs the #37 evaluation found

- tmux targets are exact (`=name`, `=name:` for panes/options): a bare
  `-t agenthub-lane-1` resolves by prefix to agenthub-lane-12 once lane 1
  is gone, so killing a finished lane could kill another.
- getRun/killRun refuse ids that are not `agenthub-lane-<n>`, so
  DELETE /api/run/main can no longer kill a user's own tmux session.
- router/apply reports restart_required only for a running pane; getRun
  returns a `gone` handle, so it was always true.
- needs_action is cleared only by the session that raised it (new nullable
  lanes.needs_action_session); a second session in the same cwd used to
  clear it on its second hook.

docs/LANES.md

@@ -738,7 +738,7 @@ This shows each lane's:
 - **status**: `running` (a session is active), `idle` (no active session), or `provisioning`
 - **liveness**: `active` (recently updated), `dead` (silent for too long), or `idle` (not expected to be running)
 - **progress**: percentage of the pipeline completed (0–100%)
-- **needs_action**: a notification if the session is blocked waiting for input
+- **needs_action**: a notification if the session is blocked waiting for input. `needs_action_session` records which session raised it, and only that session's next hook clears it — a second session in the same cwd (a hand-started terminal beside the dashboard pane) rebinds `session_id` but cannot clear a prompt it is not the one waiting on
 
 A lane row also gets a `⇢ detected:<stage>` suffix when the server's inferred
 stage (see "Stage detection" below) leads the declared `stage` shown in the