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'

docker-compose.yml

@@ -11,7 +11,7 @@ services:
       AZURE_SPEECH_REGION: "${AZURE_SPEECH_REGION:-eastus}"
       AZURE_TTS_VOICE: "${AZURE_TTS_VOICE:-en-US-Ava:DragonHDOmniLatestNeural}"
       LLM_BASE_URL: "${LLM_BASE_URL:-http://192.168.86.2:3005/api}"
-      LLM_MODEL: "${LLM_MODEL:-gemma-4-e4b}"
+      LLM_MODEL: "${LLM_MODEL:-qwen2.5-vl-3b}"
       LLM_API_KEY: "${LLM_API_KEY:-not-needed}"
       WEB_MCP_ENABLED: "${WEB_MCP_ENABLED:-true}"
       FIRECRAWL_BASE: "${FIRECRAWL_BASE:-http://192.168.86.2:3002}"