feat: serve docs flat at /<repo>/ with no redirects

- collect.py copies each repo's built site contents directly to a
  top-level <repo>/ dir (was libs|apis|wiki/<repo>/site nesting)
- nginx uses `index index.html lib/index.html api/index.html` so
  /dagpipe/ -> lib/index.html, /auth-server/ -> api/index.html are
  served internally with no redirects
- _index regenerates links against the flat layout
  (/dagpipe/lib/, /auth-server/api/, /mongo-ops/, /blog/...)
- config.yml static entries point at vendored blog/ + media-manager/
- Dockerfile copies per-repo dirs flat into the nginx html root
- removed stale libs/, apis/, wiki/, tutorials/ category trees

hexa/mcp/nav.json

@@ -0,0 +1,38 @@
+[
+  {
+    "module": "hexa",
+    "resource": "doc://modules/hexa"
+  },
+  {
+    "module": "hexa.check_matches",
+    "resource": "doc://modules/hexa.check_matches"
+  },
+  {
+    "module": "hexa.cli",
+    "resource": "doc://modules/hexa.cli"
+  },
+  {
+    "module": "hexa.container",
+    "resource": "doc://modules/hexa.container"
+  },
+  {
+    "module": "hexa.generate_abc",
+    "resource": "doc://modules/hexa.generate_abc"
+  },
+  {
+    "module": "hexa.generate_yaml",
+    "resource": "doc://modules/hexa.generate_yaml"
+  },
+  {
+    "module": "hexa.model",
+    "resource": "doc://modules/hexa.model"
+  },
+  {
+    "module": "hexa.parse_abc",
+    "resource": "doc://modules/hexa.parse_abc"
+  },
+  {
+    "module": "hexa.parse_yaml",
+    "resource": "doc://modules/hexa.parse_yaml"
+  }
+]