v0.5: hooks (cron / git push / file change)

[proofmancer]

Run an agent automatically based on a trigger.

Scope

• Schedule: cron expression per agent, served by a small in-process scheduler.
• Git: poll the workspace cwd for new commits on a branch, fire agent on change.
• File: chokidar watcher on a glob, fire agent on save.
• Each trigger run shows up in the history view (v0.2: shared MEMORY.md per workspace #3).

Out of scope

• External webhook receivers — that needs a public URL, not v0.5.