Label the dashboard session link honestly + document the Remote Control steer path

[suleimansh]

Part of #209. Follow-up to the #214 de-risk (see that issue's closing note).

Our runs are headless, which is not Remote-Controlled, so the default https://claude.ai/code link on the dashboard is a generic entry point, not a live per-run session. Right now the dashboard renders it as a "live session" anchor, which overpromises.

Scope:

• Relabel the generic default as "Open Claude Code" on the dashboard; keep "live session" only for a real user-supplied --session-link.
• Keep showing the real session id (it is the local transcript id, useful for claude --resume).
• Rewrite the README "live session" section to be accurate: headless is not Remote-Controlled; to steer live, the user starts their own claude auth login + claude --remote-control --name <run> session and opens it from claude.ai/code.

One PR, one changeset.