docs(mcp): Phase 10 — client config matrix

[erishforG]

무엇

MCP client registration doc에 Claude Desktop/Cursor config file matrix와 installer merge rules를 추가했습니다.

왜

Refs #293. v1.0 MCP registration path에서 manual setup과 future installer hook이 같은 documented target을 공유하도록 고정합니다. @erishforG

변경

• Claude Desktop macOS/Windows config file paths documented
• Cursor macOS/Linux/Windows config file paths documented
• installer merge rules: JSON parse, preserve unrelated keys, replace only git-parsec, keep command/args separate
• installer hook contract wording aligned to the documented table

다음 Phase 힌트

• opt-in installer hook can use this matrix as the source of truth
• add dry-run JSON diff once implementation begins

리스크

Low. docs/mcp only; no CLI, git, or shared MCP runtime behavior changed.

롤백

Revert this docs-only commit.

Test plan

• cargo build --quiet
• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test --quiet