Loops: user-created scheduled agent sessions only; drop the auto reconciler loops

[pallaoro]

A Loop is now one thing the user deliberately creates: on a fixed interval it starts a coding agent in a fresh task with the same prompt, on this Mac or a box (whichever engine owns the loop's project).

• Remove the auto-registered board-reconciler and the pr-ci-watcher / auto-merge-when-green templates; prune their stale rows on start. Nothing registers a loop on the user's behalf.
• One template remains: agent-session — each tick creates a fresh task (" #") and launches the chosen agent with the stored prompt, through the same task-create + spawn path as the composer (extracted into sessions.ts, shared with the dispatcher).
• Ticks skip only while the previous run has a live PTY (daemon ground truth), so a status stranded at 'running' by an exit-while-closed can't wedge the loop.
• Local vs remote: the aggregate routes loop create by the target project's engine and toggle/run-now/delete by the learned loop id; the panel labels projects and loops with their environment.
• Loops panel rewritten: name, agent, project · environment, interval (min 1m), prompt.

Note: main's auto-merge hardening (draft skip + verifyChecksGreen) is kept in merge-queue/git-core; only its deleted template caller is gone.