[extension] Add Dotdog extension to community catalog (#3558)

* Add Dotdog extension to community catalog

Add dotdog extension submitted by @logohere to:
- extensions/catalog.community.json (alphabetical order)
- docs/community/extensions.md community extensions table

Closes #3555

Assisted-by: GitHub Copilot (model: claude-sonnet-4.6, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(catalog): alphabetize dotdog entry and correct tool requirement

Assisted-by: GitHub Copilot (model: claude-opus-4.8, autonomous)

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

extensions/catalog.community.json

@@ -1248,6 +1248,47 @@
       "created_at": "2026-03-13T00:00:00Z",
       "updated_at": "2026-03-13T00:00:00Z"
     },
+    "dotdog": {
+      "name": "Dotdog",
+      "id": "dotdog",
+      "description": "Import GitHub Spec Kit artifacts into local knowledge graphs for validation, analysis, search, and MCP queries.",
+      "author": "specdog",
+      "version": "0.9.0",
+      "download_url": "https://github.com/specdog/dotdog/releases/download/v0.9.0/dotdog-spec-kit-extension-v0.9.0.zip",
+      "repository": "https://github.com/specdog/dotdog",
+      "homepage": "https://specdog.github.io/dotdog",
+      "documentation": "https://github.com/specdog/dotdog/blob/main/docs/spec-kit-extension.md",
+      "changelog": "https://github.com/specdog/dotdog/blob/main/CHANGELOG.md",
+      "license": "MIT",
+      "category": "docs",
+      "effect": "read-write",
+      "requires": {
+        "speckit_version": ">=0.12.0",
+        "tools": [
+          {
+            "name": "dotdog",
+            "version": ">=0.9.0",
+            "required": true
+          }
+        ]
+      },
+      "provides": {
+        "commands": 3,
+        "hooks": 0
+      },
+      "tags": [
+        "specification",
+        "knowledge-graph",
+        "validation",
+        "mcp",
+        "local-first"
+      ],
+      "verified": false,
+      "downloads": 0,
+      "stars": 0,
+      "created_at": "2026-07-16T00:00:00Z",
+      "updated_at": "2026-07-16T00:00:00Z"
+    },
     "ears": {
       "name": "EARS Requirements Syntax",
       "id": "ears",