feat: Register "What-if Analysis" community extension (#2182)

* feat: implement read-only what-if analysis command

* chore: polish what-if analysis (Claude hints + optional tasks)

* refactor: deliver what-if analysis as a standalone extension

* Move What-if extension to standalone repo and update community catalog

* Fix: Reorder whatif extension alphabetically in community catalog

README.md

@@ -241,6 +241,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | V-Model Extension Pack | Enforces V-Model paired generation of development specs and test specs with full traceability | `docs` | Read+Write | [spec-kit-v-model](https://github.com/leocamello/spec-kit-v-model) |
 | Verify Extension | Post-implementation quality gate that validates implemented code against specification artifacts | `code` | Read-only | [spec-kit-verify](https://github.com/ismaelJimenez/spec-kit-verify) |
 | Verify Tasks Extension | Detect phantom completions: tasks marked [X] in tasks.md with no real implementation | `code` | Read-only | [spec-kit-verify-tasks](https://github.com/datastone-inc/spec-kit-verify-tasks) |
+| What-if Analysis | Preview the downstream impact (complexity, effort, tasks, risks) of requirement changes before committing to them | `visibility` | Read-only | [spec-kit-whatif](https://github.com/DevAbdullah90/spec-kit-whatif) |
 | Worktree Isolation | Spawn isolated git worktrees for parallel feature development without checkout switching | `process` | Read+Write | [spec-kit-worktree](https://github.com/Quratulain-bilal/spec-kit-worktree) |
 
 To submit your own extension, see the [Extension Publishing Guide](extensions/EXTENSION-PUBLISHING-GUIDE.md).

extensions/catalog.community.json

@@ -1918,6 +1918,34 @@
       "created_at": "2026-03-16T00:00:00Z",
       "updated_at": "2026-03-16T00:00:00Z"
     },
+    "whatif": {
+      "name": "What-if Analysis",
+      "id": "whatif",
+      "description": "Preview the downstream impact (complexity, effort, tasks, risks) of requirement changes before committing to them.",
+      "author": "DevAbdullah90",
+      "version": "1.0.0",
+      "repository": "https://github.com/DevAbdullah90/spec-kit-whatif",
+      "homepage": "https://github.com/DevAbdullah90/spec-kit-whatif",
+      "documentation": "https://github.com/DevAbdullah90/spec-kit-whatif/blob/main/README.md",
+      "license": "MIT",
+      "requires": {
+        "speckit_version": ">=0.6.0"
+      },
+      "provides": {
+        "commands": 1,
+        "hooks": 0
+      },
+      "tags": [
+        "analysis",
+        "planning",
+        "simulation"
+      ],
+      "verified": false,
+      "downloads": 0,
+      "stars": 0,
+      "created_at": "2026-04-13T00:00:00Z",
+      "updated_at": "2026-04-13T00:00:00Z"
+    },
     "worktree": {
       "name": "Worktree Isolation",
       "id": "worktree",