docs: add per-tool API documentation and fix parity gaps

- Create 53 per-tool VitePress documentation pages with accurate
  parameters from Zod schemas, example requests, and response formats
- Add root llms.txt for LLM-friendly repo browsing
- Fix OpenAPI spec: add auth and 422 error schemas to
  edit-metadata/inspect and strip-metadata/inspect sub-routes
- Fix tool count inconsistency (52 -> 53) across landing site,
  e2e tests, and local docs
- Rename color-adjustments.ts to adjust-colors.ts to match tool ID
- Update VitePress sidebar with all 8 tool categories and top nav

apps/api/src/openapi.yaml

@@ -4300,6 +4300,12 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/UnauthorizedError"
+        "422":
+          description: Failed to read image metadata
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
 
   /api/v1/tools/edit-metadata:
     post:
@@ -4373,7 +4379,8 @@ paths:
       tags: [Tools]
       summary: Inspect metadata (ExifTool)
       description: Read all metadata from an image using ExifTool. Returns all embedded EXIF, IPTC, XMP, and GPS fields.
-      security: []
+      security:
+        - bearerAuth: []
       requestBody:
         required: true
         content:
@@ -4400,6 +4407,18 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/Error"
+        "401":
+          description: Authentication required
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/UnauthorizedError"
+        "422":
+          description: Failed to read image metadata
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
 
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