Log HEIC failure mode in AGENTS.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GGi69eKrHbfzH7FChG8CFX

AGENTS.md

@@ -21,3 +21,4 @@ Type: code
 
 ## Known failure modes
 - **crowd.skyebrowse.com showed a login form / "TypeError: Load failed" (resolved 2026-07-02).** The custom-domain proxy forwards `x-forwarded-host` but not `x-forwarded-proto`, so Gradio computed `root_url = http://crowd.skyebrowse.com` and the https page mixed-content-blocked every fetch; Gradio 6 SSR then rendered its login-form fallback (SSR also dropped `launch(head=...)` meta entirely). Fix, both required: `ssr_mode=False` in `launch()` + the `_https_get_root_url` monkeypatch in app.py (upgrades http→https for non-localhost hosts, because CSR still server-renders `theme.css`/`iframeResizer` URLs from the computed root). Do not remove either when upgrading Gradio; re-verify https://crowd.skyebrowse.com in a browser after any Gradio bump.
+- **HEIC (iPhone) uploads crashed with `PIL.UnidentifiedImageError` in Gradio preprocessing (resolved 2026-08-04, commit ab675ad).** Gradio's `image_utils.preprocess_image` calls `PIL.Image.open` even with `type="filepath"`, and stock Pillow has no HEIC decoder. Fix: `pillow-heif` in requirements.txt + `register_heif_opener()` at import time in app.py (registers globally in PIL). Verified via live-Space API call with a real .heic.