feat(view): save 2D board view to file instead of base64 (#161)

* Feat: save 2D board view to file instead of returning base64

The 2D view was returning base64-encoded image data in JSON, which
often exceeded token/message size limits. Now saves the rendered
image (PNG/JPG/SVG) next to the PCB file and returns the file path.
This makes the output usable by tools that can read image files
directly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(board): add opt-in responseMode param to get_board_2d_view

Add a responseMode string parameter (enum: inline | file, default inline)
so callers can choose how the rendered image is delivered.

- inline (default, pre-PR behavior): image bytes are base64-encoded
  and returned in the imageData response field -- backward-compatible.
- file: image is written next to the .kicad_pcb as
  <board>_2d_view.<ext> and filePath is returned -- resolves the
  MCP message-size limit problem on large boards.

Rendering logic is shared between both modes; only response packaging
differs. Updated tool schema (Python + TypeScript) and replaced the
existing test file with 5 focused unit tests covering inline/file modes
for PNG and SVG formats plus the default-is-inline contract.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

python/schemas/tool_schemas.py

@@ -228,7 +228,16 @@ BOARD_TOOLS = [
     {
         "name": "get_board_2d_view",
         "title": "Render Board Preview",
-        "description": "Generates a 2D visual representation of the current board state as a PNG image.",
+        "description": (
+            "Generates a 2D visual representation of the current board state as a PNG, JPG, or SVG image. "
+            "Use responseMode to control how the image is returned. "
+            'responseMode="inline" (default) returns the image bytes as a base64-encoded imageData '
+            "string in the JSON response — convenient for small boards but may exceed message-size limits on "
+            "large designs. "
+            'responseMode="file" writes the image next to the .kicad_pcb file as '
+            "<board>_2d_view.<ext> and returns a filePath; callers that can open local files should "
+            "prefer this mode for large boards."
+        ),
         "inputSchema": {
             "type": "object",
             "properties": {
@@ -244,6 +253,27 @@ BOARD_TOOLS = [
                     "minimum": 100,
                     "default": 600,
                 },
+                "format": {
+                    "type": "string",
+                    "enum": ["png", "jpg", "svg"],
+                    "description": "Output image format (default: png)",
+                    "default": "png",
+                },
+                "layers": {
+                    "type": "array",
+                    "items": {"type": "string"},
+                    "description": "Optional list of layer names to include; all enabled layers if omitted",
+                },
+                "responseMode": {
+                    "type": "string",
+                    "enum": ["inline", "file"],
+                    "default": "inline",
+                    "description": (
+                        "How to return the image. "
+                        '"inline" (default): base64-encoded bytes in the imageData response field. '
+                        '"file": write to <board>_2d_view.<ext> next to the PCB and return filePath.'
+                    ),
+                },
             },
         },
     },