build(docker): add worker image with ast-grep, pi, browser-use, and skills

Multi-stage build for Poimen Temporal Worker pod:

TOOLS INSTALLED:
- ast-grep (v0.24.0): semantic code pattern matching
- pi CLI: agent framework with pre-loaded skills
- browser-use CLI: browser automation & testing
- Chromium: headless browser for E2E tests
- Go 1.25: worker binary compilation

SKILLS PRE-LOADED:
- caveman: token compression (65% reduction)
- andrej-karpathy: LLM principles & training patterns
- browser-use: browser automation for T2/T3/T6/T9

VOLUMES & DIRECTORIES:
- /app/work/: ephemeral workspace for git clones
- /app/logs/: execution logs
- /app/screenshots/: test screenshots (max 2GB)
- /root/.pi/agent/skills/: pre-loaded skills

ENVIRONMENT VARIABLES:
- PI_SKILLS_PATH, AST_GREP_BIN, BROWSER_USE_BIN, CHROMIUM_BIN
- SCREENSHOTS_DIR, MEMORY_SERVICE_URL, TEMPORAL_HOSTPORT

STARTUP DIAGNOSTICS:
- Entrypoint verifies all CLI tools available
- Checks pi skills directory
- Validates browser automation readiness
- Confirms Chromium availability
- Tests memory service connectivity

IMAGE SIZE: ~500MB (optimized multi-stage build)

k8s/worker-deployment.yaml

@@ -13,8 +13,8 @@ spec:
       labels:
         app: poimen-worker
       annotations:
-        git-commit: "ea8499c"  # ✅ Updated on each push, triggers rolling restart
-        deployment-date: "2026-08-29"
+        git-commit: "166674d"  # ✅ Updated on each push, triggers rolling restart
+        deployment-date: "2026-08-30"
     spec:
       containers:
       - name: worker