Remove exec agent — replaced by OpenClaw skill + vault API (#722)

## What

Removes the exec agent (PR #697). Its functionality is replaced by:

1. **OpenClaw skill** — teaches any OpenClaw instance to be the factory's face
2. **Vault API** — structured interface for proposals, approvals, rejections

The exec agent was rebuilding OpenClaw in bash. Every piece has a native OpenClaw equivalent:
- CHARACTER.md → SOUL.md
- exec/MEMORY.md → MEMORY.md
- exec-session.sh → session management
- exec-briefing.sh → heartbeats/cron
- Matrix dispatch → channel plugins

## Why

Prudence isn't a separate agent. She's what OpenClaw becomes when it has the disinto skill. One LLM, one vault API, no LLM-to-LLM.

## Related

- #721 — remove escalation, route through vault
- #709 — skill registry research
- #466 — example project (vault should have handled this, not escalation)

Co-authored-by: openhands <openhands@all-hands.dev>
Reviewed-on: https://codeberg.org/johba/disinto/pulls/722

.woodpecker/agent-smoke.sh

@@ -82,7 +82,7 @@ while IFS= read -r -d '' f; do
     printf 'FAIL [syntax] %s\n' "$f"
     FAILED=1
   fi
-done < <(find dev gardener review planner supervisor lib vault action exec -name "*.sh" -print0 2>/dev/null)
+done < <(find dev gardener review planner supervisor lib vault action -name "*.sh" -print0 2>/dev/null)
 echo "syntax check done"
 
 # ── 2. Function-resolution check ─────────────────────────────────────────────
@@ -213,9 +213,6 @@ check_script action/action-agent.sh    dev/phase-handler.sh
 check_script supervisor/supervisor-run.sh
 check_script supervisor/preflight.sh
 check_script predictor/predictor-run.sh
-check_script exec/exec-session.sh
-check_script exec/exec-inject.sh
-check_script exec/exec-briefing.sh
 
 echo "function resolution check done"