docs: drop process records and internal implementation docs

Keep only install, usage, development-workflow and architecture-boundary
documents; remove the one-off refactor plans, audits and ledgers that had
already served their purpose.

- delete docs/refactor plus the agent API surface audit generator and its
  drift-only tests; the fixed route registry remains the source of truth
- delete internal implementation notes (agent, music, notification, transfer,
  subscription activity, docker startup, V3t runtime governance)
- delete site adapter capture/release shims and the ADR records; external
  links point at MoviePilot-Site-Collector instead
- keep docs/architecture-overview.md and gate its dependency and event
  figures against the generated fixtures
- drop doc-only assertions from the architecture baseline test and retarget
  remaining references at code and rule documents

scripts/architecture/mypy_ratchet.py

@@ -1,7 +1,7 @@
 """
 为宿主源码维护 mypy 存量债务例外清单，并保证新增文件、新增内容清零。
 
-门禁口径（与 docs/code-quality.md 保持一致）：
+门禁口径（本脚本即为口径来源）：
 
 1. 例外：基线中登记的文件是“当前未完成”的存量债务，按文件 + 错误码记录上限。
 2. 新增文件：基线未登记的文件必须零诊断，出现任何错误即失败。