Merge feat/gemma4-multimodal-support: resolve MULTIMODAL_BACKLOG.md conflict

Combined main's rich epic structure with PR #1493's Task 3/4 items.
Code changes to multimodal.py merged cleanly.

MULTIMODAL_BACKLOG.md

@@ -27,3 +27,9 @@
   - [ ] Ingest PDF research papers on agentic workflows.
   - [ ] Analyze diagrams and charts to extract structural logic.
   - [ ] Synthesize findings into `Sovereign_Knowledge_Graph.md`.
+
+## General Tasks
+
+- [x] **Task 1:** Add Gemma 4 entries to `KNOWN_MODEL_CAPABILITIES` and vision fallback chain in `src/infrastructure/models/multimodal.py`. Gemma 4 is a multimodal model supporting vision, text, tools, JSON, and streaming. ✅ PR #1493
+- [ ] **Task 3:** Add a `ModelCapability.VIDEO` enum member for future video understanding models.
+- [ ] **Task 4:** Implement `get_model_for_content("video")` routing with appropriate fallback chain.

src/infrastructure/models/multimodal.py

@@ -162,6 +162,35 @@ KNOWN_MODEL_CAPABILITIES: dict[str, set[ModelCapability]] = {
     "gemma2:2b": {ModelCapability.TEXT, ModelCapability.JSON, ModelCapability.STREAMING},
     "gemma2:9b": {ModelCapability.TEXT, ModelCapability.JSON, ModelCapability.STREAMING},
     "gemma2:27b": {ModelCapability.TEXT, ModelCapability.JSON, ModelCapability.STREAMING},
+    # Gemma 4 — multimodal (vision + text + tools)
+    "gemma4": {
+        ModelCapability.TEXT,
+        ModelCapability.VISION,
+        ModelCapability.TOOLS,
+        ModelCapability.JSON,
+        ModelCapability.STREAMING,
+    },
+    "gemma4:4b": {
+        ModelCapability.TEXT,
+        ModelCapability.VISION,
+        ModelCapability.TOOLS,
+        ModelCapability.JSON,
+        ModelCapability.STREAMING,
+    },
+    "gemma4:12b": {
+        ModelCapability.TEXT,
+        ModelCapability.VISION,
+        ModelCapability.TOOLS,
+        ModelCapability.JSON,
+        ModelCapability.STREAMING,
+    },
+    "gemma4:27b": {
+        ModelCapability.TEXT,
+        ModelCapability.VISION,
+        ModelCapability.TOOLS,
+        ModelCapability.JSON,
+        ModelCapability.STREAMING,
+    },
     # Mistral series
     "mistral": {
         ModelCapability.TEXT,
@@ -252,6 +281,7 @@ KNOWN_MODEL_CAPABILITIES: dict[str, set[ModelCapability]] = {
 # These are tried in order when the primary model doesn't support a capability
 DEFAULT_FALLBACK_CHAINS: dict[ModelCapability, list[str]] = {
     ModelCapability.VISION: [
+        "gemma4:12b",  # Gemma 4 — multimodal, fast and capable
         "llama3.2:3b",  # Fast vision model
         "llava:7b",  # Classic vision model
         "qwen2.5-vl:3b",  # Qwen vision

tests/infrastructure/test_multimodal.py

@@ -76,6 +76,10 @@ class TestKnownModelCapabilities:
             "llava",
             "moondream",
             "qwen2.5-vl",
+            "gemma4",
+            "gemma4:4b",
+            "gemma4:12b",
+            "gemma4:27b",
         ]
         for name in vision_names:
             assert ModelCapability.VISION in KNOWN_MODEL_CAPABILITIES[name], name