Add project agent run list, show, cancel, and retry

entire project agent run reads and acts on the project's agent runs through /{host}/{project}/runs:

• list prints one page, newest first, filtered by --agent and --status, with the cursor for the next page.
• show <run-id> prints the agent, change, status or failure, reading, finding count, summary, and the failure diagnostic.
• cancel <run-id> cancels a queued or running run and says when it had already finished.
• retry <run-id> starts the next attempt, with an Idempotency-Key.

Run and agent IDs must be ULIDs before any request, and --json passes the server's runs through unchanged.