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/docs/tools/image-enhancement.md

@@ -0,0 +1,92 @@
+# Image Enhancement
+
+One-click auto-improve with smart analysis. Analyzes the image and applies exposure, contrast, white balance, saturation, sharpness, and denoising corrections.
+
+## API Endpoint
+
+`POST /api/v1/tools/image-enhancement`
+
+**Processing:** Synchronous (uses `createToolRoute` factory, returns result directly)
+
+**Model bundle:** None required for basic enhancement. The `upscale-enhance` bundle (4-5 GB) is used only when `deepEnhance` is enabled (for AI noise removal via SCUNet).
+
+## Parameters
+
+| Parameter | Type | Required | Default | Description |
+|-----------|------|----------|---------|-------------|
+| file | file | Yes | - | Image file (multipart) |
+| mode | string | No | `"auto"` | Enhancement mode: `auto`, `portrait`, `landscape`, `low-light`, `food`, `document` |
+| intensity | number | No | `50` | Overall enhancement intensity (0-100) |
+| corrections | object | No | all `true` | Selective corrections to apply (see below) |
+| deepEnhance | boolean | No | `false` | Enable AI-powered noise removal (requires `noise-removal` tool installed) |
+
+### Corrections Object
+
+| Field | Type | Default | Description |
+|-------|------|---------|-------------|
+| exposure | boolean | `true` | Auto-correct exposure |
+| contrast | boolean | `true` | Auto-correct contrast |
+| whiteBalance | boolean | `true` | Auto-correct white balance |
+| saturation | boolean | `true` | Auto-correct saturation |
+| sharpness | boolean | `true` | Auto-sharpen |
+| denoise | boolean | `true` | Light denoising |
+
+## Example Request
+
+```bash
+curl -X POST http://localhost:13490/api/v1/tools/image-enhancement \
+  -F "file=@photo.jpg" \
+  -F 'settings={"mode":"portrait","intensity":70,"corrections":{"exposure":true,"contrast":true,"sharpness":false}}'
+```
+
+## Response (200 OK)
+
+```json
+{
+  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+  "downloadUrl": "/api/v1/download/{jobId}/photo_enhanced.jpg",
+  "originalSize": 300000,
+  "processedSize": 310000
+}
+```
+
+## Analyze Endpoint
+
+`POST /api/v1/tools/image-enhancement/analyze`
+
+Analyzes an image and returns correction recommendations without applying them.
+
+### Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| file | file | Yes | Image file (multipart) |
+
+### Example Request
+
+```bash
+curl -X POST http://localhost:13490/api/v1/tools/image-enhancement/analyze \
+  -F "file=@photo.jpg"
+```
+
+### Response (200 OK)
+
+```json
+{
+  "corrections": {
+    "exposure": { "value": 0.3, "direction": "brighten" },
+    "contrast": { "value": 0.2, "direction": "increase" },
+    "whiteBalance": { "value": 200, "direction": "warmer" },
+    "saturation": { "value": 0.1, "direction": "increase" },
+    "sharpness": { "value": 0.4, "direction": "sharpen" }
+  }
+}
+```
+
+## Notes
+
+- This tool uses the synchronous `createToolRoute` factory, so it returns a standard response (not 202 async).
+- The `mode` parameter adjusts how corrections are weighted (e.g., portrait mode is gentler on skin tones, landscape mode boosts saturation).
+- When `deepEnhance` is enabled and the `noise-removal` tool (SCUNet) is installed, an additional AI denoising pass is applied after the standard corrections.
+- The analyze endpoint is useful for previewing what corrections would be applied before committing.
+- Supports HEIC/HEIF, RAW, TGA, PSD, EXR, and HDR input formats via automatic decoding.