docs(phase-6): update ai_client+models guides; report + follow-up track setup

Phase 6 t6.1 + t6.2 (no archive per user directive):
- docs/guide_ai_client.md: update Overview to mention 8 providers (was 5);
  add 'Shared OpenAI-Compatible Helper' section explaining
  src/openai_compatible.py (NormalizedResponse, OpenAICompatibleRequest,
  send_openai_compatible, usage pattern); document the Qwen adapter
  and Llama multi-backend.
- docs/guide_models.md: update PROVIDERS list to 8 entries (was 5).
- conductor/tracks.md: update the Qwen track entry to reflect
  '50/79 tasks done; Phase 6 in progress; NOT archiving - has follow-up';
  add detailed status note pointing to the follow-up track + audit
  report.
- docs/reports/qwen_llama_grok_followup_audit_20260611.md: NEW report
  explaining why a follow-up is needed (7 categories of gaps; the
  Tech Lead's 'footnote for now' failure mode; the lessons learned).
- conductor/tracks/qwen_llama_grok_followup_20260611/: NEW follow-up
  track setup (spec.md, state.toml, metadata.json, TODO.md).
  5 phases: tool loop lift, PROVIDERS move, UX adaptations 2-9,
  local-first + matrix v2, Anthropic/Gemini/DeepSeek migration.

Phase 6 t6.3 (git mv to archive) and t6.4 (mark Recently Completed)
are NOT applied per user directive: 'we can then doc this we're not
archiving yet, if we have a follow up track I need this one to stay
up because there is still alot todo'.

docs/guide_models.md

@@ -363,7 +363,7 @@ The file also defines several module-level constants used across the app:
 
 ```python
 # Provider routing
-PROVIDERS: list[str] = ["gemini", "anthropic", "deepseek", "MiniMax", "gemini-cli"]
+PROVIDERS: list[str] = ["gemini", "anthropic", "gemini_cli", "deepseek", "minimax", "qwen", "grok", "llama"]
 
 # Tool categories (for Tool Bias)
 TOOL_CATEGORIES: list[str] = [