fix(vision): auto-resize oversized images, increase default timeout, fix vision capability detection

Cherry-picked from PR #7749 by kshitijk4poor with modifications:

- Raise hard image limit from 5 MB to 20 MB (matches most restrictive provider)
- Send images at full resolution first; only auto-resize to 5 MB on API failure
- Add _is_image_size_error() helper to detect size-related API rejections
- Auto-resize uses Pillow (soft dep) with progressive downscale + JPEG quality reduction
- Fix get_model_capabilities() to check modalities.input for vision support
- Increase default vision timeout from 30s to 120s (matches hardcoded fallback intent)
- Applied retry-with-resize to both vision_analyze_tool and browser_vision

Closes #7740

agent/models_dev.py

@@ -383,7 +383,14 @@ def get_model_capabilities(provider: str, model: str) -> Optional[ModelCapabilit
 
     # Extract capability flags (default to False if missing)
     supports_tools = bool(entry.get("tool_call", False))
-    supports_vision = bool(entry.get("attachment", False))
+    # Vision: check both the `attachment` flag and `modalities.input` for "image".
+    # Some models (e.g. gemma-4) list image in input modalities but not attachment.
+    input_mods = entry.get("modalities", {})
+    if isinstance(input_mods, dict):
+        input_mods = input_mods.get("input", [])
+    else:
+        input_mods = []
+    supports_vision = bool(entry.get("attachment", False)) or "image" in input_mods
     supports_reasoning = bool(entry.get("reasoning", False))
 
     # Extract limits