Restructure CLAUDE.md per official Claude Code recommendations

CLAUDE.md: 178→25 lines — commands + @ARCHITECTURE.md import only

Rules split into .claude/rules/ (load at startup, topic-scoped):
  llm-inference.md  — Bifrost-only, semaphore, model name format, timeouts
  agent-pipeline.md — tier rules, no tools in medium, memory outside loop
  fast-tools.md     — extension guide (path-scoped: fast_tools.py + agent.py)
  secrets.md        — .env keys, Vaultwarden, no hardcoding

Path-scoped rule: fast-tools.md only loads when editing fast_tools.py or agent.py

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/rules/agent-pipeline.md

@@ -0,0 +1,20 @@
+# Agent Pipeline Rules
+
+## Tiers
+- Complex tier requires `/think ` prefix. Any LLM classification of "complex" is downgraded to medium. Do not change this.
+- Medium is the default tier. Light is only for trivial static-knowledge queries matched by regex or LLM.
+- Light tier upgrade to medium is automatic when URL content is pre-fetched or a fast tool matches.
+
+## Medium agent
+- `_DirectModel` makes a single `ainvoke()` call with no tool schema. Do not add tools to the medium agent.
+- `qwen3:4b` behaves unreliably when a tool array is present in the request — inject context via system prompt instead.
+
+## Memory
+- `add_memory` and `search_memory` are called directly in `run_agent_task()`, outside the agent loop.
+- Never add memory tools to any agent's tool list.
+- Memory storage (`_store_memory`) runs as an asyncio background task after the semaphore is released.
+
+## Fast tools
+- `FastToolRunner.run_matching()` runs in the pre-flight `asyncio.gather` alongside URL fetch and memory retrieval.
+- Fast tool results are injected as a system prompt block, not returned to the user directly.
+- When `any_matches()` is true, the router forces medium tier before LLM classification.