feat: add category and effect as first-class fields in extension schema

.github/skills/add-community-extension/SKILL.md

@@ -70,6 +70,8 @@ Use the existing entries as the format template. Required fields:
     "documentation": "<documentation>",
     "changelog": "<changelog>",
     "license": "<license>",
+    "category": "<category>",
+    "effect": "<effect>",
     "requires": {
       "speckit_version": "<speckit_version>"
     },
@@ -87,6 +89,9 @@ Use the existing entries as the format template. Required fields:
 }
 ```
 
+**Category** — free-form string; common values: `docs`, `code`, `process`, `integration`, `visibility`
+**Effect** — one of: `read-only`, `read-write`
+
 If the extension has optional tool dependencies, add a `"tools"` array inside `"requires"`:
 
 ```json
@@ -113,8 +118,8 @@ Determine the category and effect from the extension's behavior:
 | <Name> | <Description> | `<category>` | <Effect> | [<repo-name>](<repository-url>) |
 ```
 
-**Category** — one of: `docs`, `code`, `process`, `integration`, `visibility`
-**Effect** — `Read-only` (produces reports only) or `Read+Write` (modifies project files)
+**Category** — free-form; common values: `docs`, `code`, `process`, `integration`, `visibility`
+**Effect** — write canonical values `read-only` or `read-write` in `extension.yml` and `catalog.community.json`; use `Read-only`/`Read+Write` only for the docs table display
 
 ### 6. Commit, push, and open PR
 

docs/community/extensions.md

@@ -7,18 +7,21 @@
 
 The following community-contributed extensions are available in [`catalog.community.json`](https://github.com/github/spec-kit/blob/main/extensions/catalog.community.json):
 
-**Categories:**
+**Categories** (common values, but any string is allowed):
 
 - `docs` — reads, validates, or generates spec artifacts
 - `code` — reviews, validates, or modifies source code
 - `process` — orchestrates workflow across phases
 - `integration` — syncs with external platforms
 - `visibility` — reports on project health or progress
 
-**Effect:**
+**Effect** (canonical `extension.yml`/catalog values):
 
-- `Read-only` — produces reports without modifying files
-- `Read+Write` — modifies files, creates artifacts, or updates specs
+- `read-only` — produces reports without modifying files (displayed as `Read-only` in the table)
+- `read-write` — modifies files, creates artifacts, or updates specs (displayed as `Read+Write` in the table)
+
+> [!TIP]
+> Extension authors can declare `category` and `effect` in their `extension.yml` under the `extension:` block. These fields are also available in `catalog.community.json` for tooling and the CLI (`specify extension info`).
 
 | Extension | Purpose | Category | Effect | URL |
 |-----------|---------|----------|--------|-----|