feat: add autonomous maintenance agent fleet with shared engine and validator

Add the `agents/` directory containing a fleet of autonomous AI maintenance agents for codebase consistency, including a shared async engine (`agent.py`), a dependency-free validator (`validator.py`), and specialized agents for security, audit, docs, style, frontend, SEO, test coverage, and more. Wire the fleet into the Makefile with `--fix`/`--check` modes, document the architecture in `AGENTS.md`, `CLAUDE.md`, and `README.md`, and enforce a hard rule that the `agents/` directory itself is off-limits to any code modification to preserve detection data.

Makefile

@@ -128,3 +128,63 @@ deploy:
 	git checkout production
 	git merge master
 	git push origin production
+
+# ---------------------------------------------------------------------------
+# Code validation. Dependency-free, no external tools: Python ast+py_compile,
+# JavaScript node --check, CSS brace balance, HTML/Jinja template parse.
+# ---------------------------------------------------------------------------
+.PHONY: validate
+
+validate:
+	python -m agents.validator .
+
+# ---------------------------------------------------------------------------
+# Maintenance agent fleet (see agents.md). Default mode is fix; pass CHECK=1
+# for read-only reporting with a non-zero exit on findings.
+#   make audit-agent          # autonomous fix
+#   make audit-agent CHECK=1   # report only
+#   make agents-all            # run the whole fleet
+#   make maestro               # talk to the conductor; it runs the rest
+# ---------------------------------------------------------------------------
+CHECK ?=
+AGENT_MODE := $(if $(CHECK),--check,--fix)
+
+.PHONY: security-agent audit-agent devii-agent docs-agent fanout-agent \
+        dry-agent style-agent frontend-agent seo-agent test-agent \
+        agents-all maestro
+
+security-agent:
+	python -m agents.security $(AGENT_MODE)
+
+audit-agent:
+	python -m agents.audit $(AGENT_MODE)
+
+devii-agent:
+	python -m agents.devii $(AGENT_MODE)
+
+docs-agent:
+	python -m agents.docs $(AGENT_MODE)
+
+fanout-agent:
+	python -m agents.fanout $(AGENT_MODE)
+
+dry-agent:
+	python -m agents.dry $(AGENT_MODE)
+
+style-agent:
+	python -m agents.style $(AGENT_MODE)
+
+frontend-agent:
+	python -m agents.frontend $(AGENT_MODE)
+
+seo-agent:
+	python -m agents.seo $(AGENT_MODE)
+
+test-agent:
+	python -m agents.test_coverage $(AGENT_MODE)
+
+agents-all:
+	python -m agents.orchestrator $(AGENT_MODE)
+
+maestro:
+	python -m agents.maestro