Remove imagegen-api test files from git tracking

These are local test files like imagegen.dot/imagegen.toml.
They live in gitignored tmp/ and don't need to be tracked.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tmp/imagegen-api.dot

@@ -1,11 +0,0 @@
-digraph ImageGen {
-    graph [goal="A cute robot painting a landscape"]
-    rankdir=LR
-
-    start [shape=Mdiamond, label="Start"]
-    exit  [shape=Msquare, label="Exit"]
-
-    generate [label="Generate Image", prompt="Generate an image of: $goal\n\nUse the shell tool to call the Gemini image generation API.\nThe GEMINI_API_KEY env var is already set in your environment.\n\nSteps:\n1. Use the shell tool to run: echo GEMINI_API_KEY is set: ${#GEMINI_API_KEY} chars\n2. Then run a curl command to POST to https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-image:generateContent with the API key as query param.\n   Pass JSON body with contents/parts/text for the prompt and generationConfig with responseModalities TEXT and IMAGE.\n3. Extract base64 image data from response using jq, decode with base64 -d, save to generated.png\n4. Verify with ls -la generated.png"]
-
-    start -> generate -> exit
-}

tmp/imagegen-api.toml

@@ -1,9 +0,0 @@
-version = 1
-goal = "A cute robot painting a landscape"
-graph = "imagegen-api.dot"
-
-[sandbox]
-provider = "daytona"
-
-[sandbox.env]
-GEMINI_API_KEY = "${env.GEMINI_API_KEY}"