Add LLM key-hunter toolkit, vault, and skill

- tools/scripts/llm-key-hunter: GitHub leak hunting pipeline (hunt_*,
  pivot miner, two-layer verify/content caches, per-provider verification)
- usable_keys: verified key vault across 12 providers (deepseek, minimax,
  volcanoark, longcat, codingplan, zhipu free-tier, mimo, siliconflow, etc.)
- .grok/skills/llm-key-hunter: operator skill for the hunt/verify/vault flow
- NewAPI channel import scripts and CDP capture helpers
- Result verdict buckets (excluding multi-GB blob caches and dedup dumps)

tools/scripts/llm-key-hunter/usable_keys/longcat/PLAN_SUMMARY.txt

@@ -0,0 +1,7 @@
+Meituan LongCat (美团龙猫)
+=========================
+Key prefix: ak_ (32-char total)
+Endpoint:   https://api.longcat.chat/openai
+Anthropic:  https://api.longcat.chat/anthropic
+Usable keys: 7
+Model: LongCat-2.0 (1.6T MoE, 1M context)