fix: chore(26a): delete action-agent.sh, action-poll.sh, and action/AGENTS.md (#65)

- Delete action/ directory and all its contents
- Remove action-bot from bin/disinto bot token mapping and collaborator lists
- Remove FORGE_ACTION_TOKEN from lib/env.sh and .env.example
- Remove action-bot from FORGE_BOT_USERNAMES in lib/env.sh and .env.example
- Update .woodpecker/agent-smoke.sh to remove action script checks
- Update AGENTS.md: remove action agent from description and table
- Update lib/AGENTS.md: remove action-agent references from sourced by columns
- Update docs/PHASE-PROTOCOL.md: remove action-agent reference
- Update docs/AGENT-DESIGN.md: remove action-agent from agent table
- Update planner/AGENTS.md: update action formula execution reference
- Update README.md: update formula-driven execution reference

Part of #26 — retire action-agent system.

docs/AGENT-DESIGN.md

@@ -114,4 +114,3 @@ When reviewing PRs or designing new agents, ask:
 | gardener | 1242 (agent 471 + poll 771) | Medium — backlog triage, duplicate detection, tech-debt scoring | Poll is heavy orchestration; agent is prompt-driven |
 | vault | 442 (4 scripts) | Medium — approval flow, human gate decisions | Intentionally bash-heavy (security gate should be deterministic) |
 | planner | 382 | Medium — AGENTS.md update, gap analysis | Tmux+formula (done, #232) |
-| action-agent | 192 | Light — formula execution | Close to target |

docs/PHASE-PROTOCOL.md

@@ -117,7 +117,7 @@ signal to the phase file.
 - **Post-loop exit handler (`case $_MONITOR_LOOP_EXIT`):** Must include an
   `idle_prompt)` branch. Typical actions: log the event, clean up temp files,
   and (for agents that use escalation) write an escalation entry or notify via
-  vault/forge. See `dev/dev-agent.sh`, `action/action-agent.sh`, and
+  vault/forge. See `dev/dev-agent.sh` and
   `gardener/gardener-agent.sh` for reference implementations.
 
 ## Crash Recovery