[codeforester]

Summary

• Add basectl gh review fetch for detached PR-review worktrees backed by refs/base-review/pr/<number>/<slug>.
• Add basectl gh review prune, dry-run by default, with ownership, cleanliness, detached-state, ref/head, and current PR-state checks before removal.
• Keep legacy local pr-* refs explicitly out of the permanent workflow; they remain a one-time audited cleanup.

Issue

Fixes #2623

Validation

• bats cli/bash/commands/basectl/tests/gh-review.bats
• Full source-checkout BATS suite: 1,067 passed.
• Full Python suite: 1,828 passed.
• Stability, command-reference, and documentation-link checks: 25 passed after enrolling the new stable commands.
• shellcheck cli/bash/commands/basectl/subcommands/gh_review.sh
• git diff --check

Docs Impact

• Updated docs/github-workflow.md, docs/command-reference.md, and the basectl command README.
• Updated Bash/Zsh completions and their parity tests.
• Updated the stable compatibility fixture for the two new public commands.