feat: ship production deploy, Playwright e2e, and agent implementer

Add Docker atomic deploy tooling, CI, Playwright smoke/visual suite,
shared industrial theme, physics invariants, quality-mode wiring,
and a worktree-isolated agent implementer MVP with hard safety limits.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/AGENT_IMPLEMENTER_MVP.md

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+# Implementer MVP (worktree-isolated)
+
+**Status:** Implemented in `agent/cli.mjs`  
+**Date:** 2026-07-15  
+
+Safe, deterministic Implementer cycle that **does not** require an external LLM.  
+Patches run only inside a git worktree. The agent **never** merges to `main`, **never** deploys, and **never** pushes.
+
+---
+
+## Commands
+
+| Command | Purpose |
+| ------- | ------- |
+| `dry-run` | Plan only (baseline + propose) |
+| `run-once` | Verify baseline only (no patches) |
+| `implement [--task <path>]` | Full Implementer cycle |
+| `start` | Same as implement, but requires `AUTONOMOUS_AGENT_ENABLED=true` |
+| `status` / `stop` / `resume` / `pause` / `report` | Control plane |
+
+```bash
+# Recommended successful demo cycle
+node agent/cli.mjs implement --task agent/tasks/demo-docs.json
+
+# Or via helper script
+bash scripts/agent-implement.sh --task agent/tasks/demo-docs.json
+
+# Gated continuous entry (still one cycle in MVP)
+AUTONOMOUS_AGENT_ENABLED=true node agent/cli.mjs start --task agent/tasks/demo-docs.json
+```
+
+---
+
+## Implementer cycle
+
+1. **Watchdog** — kill switch, single lock, disk, load, memory  
+2. **Plan** — load task JSON (default: `agent/tasks/demo-docs.json`)  
+3. **Validate policy** — allowlist only: `docs`, `tests`, `data-testid`, `a11y`, `small-ui`, `logging-scripts`  
+4. **Create worktree** — `.agent/worktrees/<run-id>` on branch `agent/<run-id>/<task-slug>`  
+5. **Apply bounded patch** — e.g. create `docs/AGENT_CYCLE_DEMO.md`  
+6. **Enforce limits** — ≤12 files, ≤800 diff lines, ≤25 min cycle  
+7. **Verify** — `npm test && npm run build` inside the worktree  
+8. **Score + decide** — `ACCEPT_CANDIDATE` or `REJECT`  
+9. **Report** — `agent/reports/<run-id>.json` (+ `latest.json`)
+
+### On REJECT
+
+- Remove worktree  
+- Delete local agent branch  
+- Keep the JSON report  
+
+### On ACCEPT_CANDIDATE
+
+- Keep worktree + branch  
+- Print manual review instructions  
+- Human must cherry-pick / merge into a feature branch if desired  
+
+---
+
+## Watchdog
+
+| Check | Fail condition |
+| ----- | -------------- |
+| Lock | `agent/state/agent.lock` held by a live PID (second agent refused) |
+| Kill switch | `agent/state/KILL` present |
+| Disk | `df /` usage **> 85%** |
+| Load | loadavg 1m **> nproc** |
+| Memory | MemAvailable **< 1 GiB** |
+
+```bash
+node agent/cli.mjs stop     # write KILL
+node agent/cli.mjs resume   # clear KILL
+node agent/cli.mjs status   # lock + watchdog snapshot
+```
+
+---
+
+## Example task
+
+`agent/tasks/demo-docs.json` — docs-only safe demo:
+
+- Policy: `docs`  
+- Patch: create `docs/AGENT_CYCLE_DEMO.md`  
+- No source / physics / deploy / `.env` changes  
+
+---
+
+## Limits (also in `LIMITS` in `cli.mjs`)
+
+| Limit | Value |
+| ----- | ----: |
+| max cycle | 25 min |
+| max files | 12 |
+| max diff lines | 800 |
+| parallel agents | 1 |
+
+Hard forbids: merge to main, production deploy, push, secret/`.env` access.
+
+---
+
+## Manual review after ACCEPT
+
+```bash
+# Inspect
+cat agent/reports/latest.json
+git -C .agent/worktrees/<run-id> show HEAD
+
+# Accept into your feature branch yourself (example)
+git cherry-pick <agent-commit-sha>
+
+# Or discard
+git worktree remove --force .agent/worktrees/<run-id>
+git branch -D agent/<run-id>/demo-docs
+```
+
+---
+
+## What this MVP does **not** do
+
+- Call external LLMs  
+- Modify production nginx/docker/deploy  
+- Touch `.env`  
+- Auto-merge or auto-deploy  
+- Change demo physics (prefer docs-only demo task)