Worktree 0.5.1

Worktree 0.5.1 moves the repository onto current shared gate, protocol and documentation pins.

• The shared source gate runs at Gates db7edb1, which downloads the Gates 0.1.7 release instead of 0.1.3.
• .engineering/project.yaml points at AEP protocol sources 733dbea.
• The documentation bundle action is pinned at Docs System 339b4b8, and a read-only per-source documentation check runs on pull requests and main pushes.

No library, CLI, wire-protocol, schema or behavior change; every declared surface version is unchanged.

Install: cargo install --git https://github.com/beyond10x/worktree --tag 0.5.1 b10x-worktree-cli

Validation: task check passed (fmt, Clippy -D warnings, 88 tests, generated-skill check). Required checks gate, common / Security and privacy and b10x-docs-check passed on PR #10.