Remove gt polecat done/reset/finish/sleep commands (idle producers)

These commands transitioned polecats to idle state, violating the transient
model. From PRIMING.md: "Polecats exist only while working. One task, then nuked."

Removed:
- gt polecat done - marked polecat as done and returned to idle
- gt polecat reset - force reset polecat to idle state
- gt polecat finish - alias for done
- gt polecat sleep - deprecated transition to done state
- gt polecat wake - deprecated transition to working state
- Manager.Finish() method
- Manager.Reset() method
- Manager.Wake() method
- Manager.Sleep() method

The correct model is: polecats use 'gt done' which signals Witness for nuke.
There is no "return to idle" - only death.

(gt-32d4a)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/mail-protocol.md

@@ -25,7 +25,7 @@ MR: <mr-id>          # if exit=MERGED
 Branch: <branch>
 ```
 
-**Trigger**: `gt polecat done` command generates this automatically.
+**Trigger**: `gt done` command generates this automatically.
 
 **Handler**: Witness creates a cleanup wisp for the polecat.