Revert reviewer isolation from #2598

Reviewers lose the project's CLAUDE.md, skills, MCP servers and hooks under isolation, which made reviews noticeably worse. Reviews of other people's code get an approval gate instead, in the following commits.

This reverts commit 30fa2a79ffe2c269914b036df62084ba25c94921, reversing changes made to ba41caf7b0b40cdbdc0ea8b473c3256bf34b463b.

Entire-Checkpoint: 01M471N6R56PC26S8NT474CMG1