docs(security): LLM07 named residual risk — injection classifier coverage gap

docs(security): tighten LLM02 'mitigations span' framing and collapse LLM05 to three checks

docs(security): address gate-review findings (preamble closing, LLM03 link, LLM05 count, LLM07 subjunctive)

docs(security): restore LLM05 DECISIONS link, trim LLM06/07 to fit 800-word ceiling

docs(security): fix LLM07 dangling rate-limit citation and LLM01 tool-name inconsistency

docs(security): restore LLM01/LLM02 specificity, add LLM09 orchestrator link, trim to ≤800 words

docs(security): add SECURITY.md with OWASP LLM Top 10 (2025) mapping