Harden maintainer-preview harness and review fixes

Unify conversational domain routing, preserve artifact completion evidence, replace provisional tool-round prose with terminal synthesis, and resolve verified maintainer review findings across search, frontend module identity, path policy, configuration, and built-in skill startup.

src/chat_helpers.py

@@ -50,6 +50,9 @@ _VISION_MODEL_KEYWORDS = (
     # Qwen3.5 is a natively multimodal family even when a served-model alias
     # omits the traditional "VL" suffix (for example qwen35-9b-base-native).
     "qwen3.5", "qwen3_5", "qwen35",
+    # The hosted Flash alias accepts images despite lacking a vision/VL suffix.
+    # Keep this exact: deepseek-v4-pro on the same provider is text-only.
+    "deepseek-flash",
     # multimodal families whose names don't contain "vision"/"vl" but DO accept
     # images — without these the image is silently dropped for common Ollama tags
     # like gemma3:4b or gemma4:12b (issue #1274). Gemma 3/4 (4b+), Llama 4 (all),