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.

devplacepy/static/css/landing.css

@@ -304,3 +304,58 @@
         gap: 0.375rem;
     }
 }
+
+.landing-bots-intro {
+    max-width: 760px;
+    margin: 0 0 1.5rem;
+    color: var(--text-secondary);
+    line-height: 1.6;
+}
+
+.landing-bots-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
+    gap: 1rem;
+}
+
+.landing-bot-card {
+    background: var(--bg-card);
+    border: 1px solid var(--border);
+    border-radius: var(--radius-xl);
+    padding: 1.25rem;
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+}
+
+.landing-bot-card:hover {
+    transform: translateY(-2px);
+    box-shadow: var(--shadow-lg);
+}
+
+.landing-bot-card-lead {
+    border-color: var(--accent);
+}
+
+.landing-bot-icon {
+    font-size: 1.75rem;
+}
+
+.landing-bot-card h3 {
+    margin: 0;
+    color: var(--text-primary);
+    font-size: 1.05rem;
+}
+
+.landing-bot-card p {
+    margin: 0;
+    color: var(--text-secondary);
+    font-size: 0.9rem;
+    line-height: 1.5;
+}
+
+@media (max-width: 480px) {
+    .landing-bots-grid {
+        grid-template-columns: 1fr;
+    }
+}