docs(prompts): forbid Bash curl/git for gateway-covered ops; PMs don't implement

Live smoke runs showed agents reaching for `Bash curl /api/...` and
`Bash git ...` even though the slim role prompts named the gateway
verbs, and main_pm took ownership of an implementation task and tried
to commit code from the PM seat.

- base.md and every role prompt: explicit ground rule that direct
  curl-to-orchestrator and raw-git invocations are forbidden — every
  commit/push/PR/transition/journal/comms call goes through the gateway
  verbs. The deny-list line in base.md now also covers curl/wget to the
  orchestrator's /api/... (was GitHub-only before).
- main_pm.md and cell_pm.md: explicit "you do not implement tasks
  yourself" rule. Implementation belongs to developers; PMs delegate.

agents/prompts/roles/board.md

@@ -15,6 +15,7 @@ You provide strategic oversight at the org level (Product Owner, Head of Marketi
 - `i_am_idle()`
 
 ## Ground rules
+- **Do not use `Bash curl http://...orchestrator...` or `Bash git ...` for actions the gateway covers** — triage/escalate/journal/comms all go through the gateway verbs (`triage`, `escalate_to_ceo`, `note`, `say`, `dm`, `evidence`). Direct API calls bypass tracing and will be rejected by the role gates.
 - Strategic decisions go to CEO. Don't make merge calls (PMs do that).
 - Auditor is silent: no `say`/`dm`. Log observations with `note(scope='reflect')`.
 - Errors include a `remediate` field — follow it.