Rename /debug-assistant to /debug-agent and add demo-scripting mode (#1026)

* Rename /debug-assistant to /debug-agent and add demo-scripting mode

Assistants are now called "agents" in the app, so rename the command to
match. Beyond the rename, add a "demo" mode that generates a user<->agent
conversation transcript and then drives both sides - the agent via the CLI
serve loop's FIFO, the user via the iOS simulator's composer - paced for a
recorded product demo.

Includes a sample transcript (demos/fitness-trainer.demo.yaml) and gitignores
demo recordings (demos/*.mov).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Refresh /debug-agent doc for dev drift since PR was opened

Verified the command's technical claims against current dev + the convos
CLI. The attestation/verification, contacts-list, contact-card, and CLI
serve-protocol claims all still hold; these are the drifted spots:

- Things tab (#1096): now shows *every* agent HTML thing per conversation,
  each titled by the artifact's HTML <title> — note this and point demos at
  a meaningful <title>.
- NUX empty-state mock filename: mock-thing-plan.html is gone; point at the
  current mock-thing-{countdown,dinner,pushups}.html under Empty State/Mock Data.
- Serve startup ProfileUpdate isn't metadata-free: it carries attestation
  metadata (from --attestation-*), just not the custom join-time fields.
- Contacts-list gate is verified AND templateId, not templateId alone.
- AgentContactCard -> AgentContactCardView.
- [Attestation] cached-result log line includes "agent <id>" and is debug-level.
- Mention the new "made you a thing" preview/push copy (#1073) as a demo signal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: yewreeka