Restore read-only shell to PR review (grep, cat, head, tail)

[gobetti]

Description

The review's --allowedTools was added in 834a453 (#12) to grant git commands for PR analysis — the commit describes it as "grants Claude access to git commands," and before it there was no --allowedTools at all, so the action ran on its permissive default set (which includes general Bash). But --allowedTools is an exclusive whitelist: the moment it's set, everything not listed is denied. So that change silently dropped grep, cat, and general Bash. The denial was a side effect of the flag's semantics, not a deliberate least-privilege decision.

The cost shows up now that reviews run on Sonnet 5: it still reaches for shell grep (including git show … | grep to search a specific blob version) when verifying findings across files, and each denied call burns a review turn plus a retry. On repos with a tight max_turns that waste contributes to error_max_turns failures.

This adds the read-only inspection commands back to the allow-list (grep, cat, head, tail, wc) so those calls execute instead of being denied. sed and find are intentionally left out (sed -i can write; find / can walk the whole filesystem). Builds, tests, installs, file edits, and network remain unlisted and therefore still denied — the blast radius is unchanged, since these commands only re-expose what the Read and Grep tools already permit over the same checkout. The prompt's now-contradictory "don't use shell grep" steer is dropped to match.

Ticket

N/A — ad hoc infra fix, not tied to a ticket.

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Testing Done

Changes only the review workflow's allow-list and prompt (no functional or schema change). Reproducing failing reviews locally with the restricted tool-set showed Sonnet 5 making shell grep calls that the current allow-list denies (matching the permission_denials_count in those runs); the added commands remove that denial class. Will confirm on live PR reviews by watching denial counts drop.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation as needed