prompts: add tools-image.md for image_read tool

prompts/tools-image.md

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+# Image Tools
+
+Read and interpret image files using vision capabilities. Use `call_tool`.
+
+**Dependencies**: Python 3, Pillow (for PNG resizing when over budget).
+
+---
+
+## image_read
+
+Read an image file and return it as a visual content block for interpretation. Automatically recompresses/resizes PNGs exceeding 128 KB.
+
+**Args**: `[path]` or `[path, --flags...]`
+
+Flags: `--region=x,y,w,h` (crop region), `--scale=N` (scale factor), `--quality=N` (compression quality)
+
+```
+call_tool: calls=[{tool: "image_read", args: ["/abs/path/to/image.png"]}]
+call_tool: calls=[{tool: "image_read", args: ["/abs/path/to/screenshot.png", "--region=0,0,800,600"]}]
+call_tool: calls=[{tool: "image_read", args: ["/abs/path/to/diagram.png", "--scale=0.5"]}]
+```
+
+**Returns**: Image content block (base64-encoded) that the model can see and interpret, plus a text summary with filename, size, and MIME type.
+
+**Constraints**:
+- Absolute paths only.
+- File must exist.
+- Budget: 128 KB max after recompression. Large PNGs are progressively scaled down (75% → 50% → 35% → 25%) until they fit.
+- Supported formats: any format with a recognized MIME type (PNG, JPEG, GIF, WebP, SVG, BMP, etc.).
+
+---
+
+## When to use
+
+- **Interpret visual content**: diagrams, charts, UI mockups, error screenshots, handwritten notes.
+- **Verify rendered output**: check that generated HTML/CSS/SVG looks correct.
+- **Read text from images**: OCR-like extraction from screenshots or scanned documents.
+- **Debug UI issues**: capture with `gui_screenshot`, then read with `image_read`.
+
+```
+# Capture then interpret workflow
+call_tool: calls=[{tool: "gui_screenshot", args: ["active", "--output=/tmp/debug.png"]}]
+call_tool: calls=[{tool: "image_read", args: ["/tmp/debug.png"]}]
+```
+
+**Note**: `image_read` makes the image visible to the model. Without it, image files are just opaque byte blobs. Use it any time you need to *see* what an image contains.