Initial TrueGrowth source import

tools/whistle/README.md

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+# Whistle Base64 Image Mock
+
+This folder contains a Whistle ruleset for reproducing image-model responses
+that return raw base64 image payloads instead of normal remote URLs.
+
+## Files
+
+- `mock-image-base64.rules`: paste this into Whistle Rules.
+
+## Supported scenarios
+
+- `__mock_b64_single__`: returns one image in `data[0].b64_json`
+- `__mock_b64_duplicate__`: returns two identical images in `data[].b64_json`
+- `__mock_b64_url_field__`: returns one image whose raw base64 is placed in `data[0].url`
+
+## How to use
+
+1. Open Whistle and paste the contents of `mock-image-base64.rules` into the
+   Rules editor.
+2. Make sure HTTPS capture is enabled for `api.tu-zi.com`.
+3. In AITU, keep the image Base URL pointed at `https://api.tu-zi.com/v1`
+   unless you intentionally use another domain.
+4. Add one of the marker strings above to the prompt text and submit an image
+   generation request.
+
+## Notes
+
+- The rules match both `/v1/images/generations` and `/images/generations`.
+- If you use a non-default API host, replace `api.tu-zi.com` in the rules.
+- If you want to stress-test large payload handling, replace the embedded
+  base64 string with the real raw payload from your captured response text.
+- The duplicate scenario is useful for verifying that identical base64 payloads
+  are deduplicated into the same local cache file.