feat: default to qwen2.5-vl-3b and cap tool schema length constraints

- Default LLM_MODEL to qwen2.5-vl-3b across agent, task worker, tests,
  compose, workflow, and docs
- Cap min/max length-style constraints in tool schemas to 1000 before
  LLM requests; llama.cpp rejects grammar repetitions >= 2000 and the
  memory MCP's update_note body maxLength (200000) broke qwen2.5-vl-3b
  with 'Failed to initialize samplers: failed to parse grammar'

.gitea/workflows/rebuild.yml

@@ -41,7 +41,7 @@ jobs:
             -e AZURE_SPEECH_REGION=eastus \
             -e AZURE_TTS_VOICE=en-US-Ava:DragonHDOmniLatestNeural \
             -e LLM_BASE_URL=http://192.168.86.2:3005/api \
-            -e LLM_MODEL=gemma-4-e4b \
+            -e LLM_MODEL=qwen2.5-vl-3b \
             -e LLM_API_KEY=sk-4e9259e3bd56472db57fd40adf0fe567 \
             -e WEB_MCP_ENABLED=true \
             -e FIRECRAWL_BASE=http://192.168.86.2:3002 \