Add archify skill (v2.14), pi-mermaid ext (v0.3.0), project-diagramming-mermaid + project-diagramming-archify skills

- skills/archify: vendored tt-a1i/archify 2.14.0 (MIT), pure Node 18+, zero deps
- extensions/pi-mermaid: renders mermaid blocks as ASCII in TUI; deps beautiful-mermaid + mermaid
- skills/project-diagramming-*: orchestration skills, per-project docs/ convention

skills/archify/scripts/render-examples.mjs

@@ -0,0 +1,26 @@
+// Re-render every bundled example from its JSON IR. Installed skills keep HTML
+// beside the JSON examples; the development script passes the golden directory.
+
+import { execFileSync } from 'node:child_process';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const skillRoot = path.resolve(__dirname, '..');
+const outputRoot = path.resolve(process.argv[2] || path.join(skillRoot, 'examples'));
+
+const TARGETS = [
+  ['workflow', 'agent-tool-call.workflow.json', 'workflow-agent-tool-call-rendered.html'],
+  ['sequence', 'cache-miss-request.sequence.json', 'sequence-cache-miss-request.html'],
+  ['dataflow', 'product-analytics.dataflow.json', 'dataflow-product-analytics.html'],
+  ['lifecycle', 'agent-run.lifecycle.json', 'lifecycle-agent-run.html'],
+  ['architecture', 'web-app.architecture.json', 'web-app-rendered.html'],
+];
+
+for (const [mode, input, output] of TARGETS) {
+  execFileSync(process.execPath, [
+    path.join(skillRoot, `renderers/${mode}/render-${mode}.mjs`),
+    path.join(skillRoot, 'examples', input),
+    path.join(outputRoot, output),
+  ], { stdio: 'inherit' });
+}