agents: Update PR review range to use merge base

- Changed references from `<base_remote>/<base>..HEAD` to `<merge_base>..HEAD`
  across documentation, scripts, and prompts to align with Git best practices.
- Updated `SKILL.md`, `review-checklist.md`, and agent configuration to reflect
  this change.
- Revised shell scripts (`collect_pr_context.sh` and `review_range.sh`) to
  compute and use `merge-base` for the review range.

Assisted-by: Codex

Author: datalogics-kam

.agents/skills/pr-review-auditor/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: pr-review-auditor
-description: Review the currently checked-out PR by discovering its upstream base branch with GitHub CLI, diffing base..HEAD, and performing a correctness-first code review that enforces repository policy with special priority on *GUIDELINES*.md rules and then AGENTS.md. Use when asked to do a full PR review, /review-style audit, commit-range quality check, or policy-compliance review of branch changes.
+description: Review the currently checked-out PR by discovering its upstream base branch with GitHub CLI, diffing merge-base..HEAD, and performing a correctness-first code review that enforces repository policy with special priority on *GUIDELINES*.md rules and then AGENTS.md. Use when asked to do a full PR review, /review-style audit, commit-range quality check, or policy-compliance review of branch changes.
 ---
 
 # PR Review Auditor
@@ -20,7 +20,7 @@ policy precedence: `*GUIDELINES*.md` before `AGENTS.md`.
 - checked-out branch,
 - PR number and base branch (via `gh pr view`),
 - merge-base commit,
-- review range (`<base_remote>/<base>..HEAD`),
+- review range (`<merge_base>..HEAD`),
 - changed files,
 - available policy files (`*GUIDELINES*.md`, `AGENTS.md`).
 

.agents/skills/pr-review-auditor/agents/openai.yaml

@@ -1,4 +1,4 @@
 interface:
   display_name: "PR Review Auditor"
-  short_description: "Review base..HEAD with GUIDELINES-first policy checks."
-  default_prompt: "Use $pr-review-auditor to review the current PR from upstream base to HEAD with findings-first output and strict GUIDELINES/AGENTS compliance checks."
+  short_description: "Review merge-base..HEAD with GUIDELINES-first policy checks."
+  default_prompt: "Use $pr-review-auditor to review the current PR from merge-base to HEAD with findings-first output and strict GUIDELINES/AGENTS compliance checks."

.agents/skills/pr-review-auditor/references/review-checklist.md

@@ -8,7 +8,7 @@
 
 ## Review Scope
 
-- Determine PR base branch and audit `<base_remote>/<base>..HEAD`.
+- Determine PR base branch, compute merge-base, and audit `<merge_base>..HEAD`.
 - Review full commit messages, changed files, and relevant patches.
 - Focus on behavior, CI impact, tests, then style.
 

.agents/skills/pr-review-auditor/scripts/collect_pr_context.sh

@@ -62,7 +62,7 @@ fi
 rm -f "${fetch_error_file}"
 
 merge_base="$(git merge-base "${base_remote}/${base_ref}" HEAD)"
-review_range="${base_remote}/${base_ref}..HEAD"
+review_range="${merge_base}..HEAD"
 
 echo "CONTEXT_SOURCE=${context_source}"
 echo "PR_NUMBER=${pr_number}"

.agents/skills/pr-review-auditor/scripts/review_range.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 range="${1:-}"
 if [[ -z "${range}" ]]; then
     echo "usage: $(basename "$0") <git-range>" >&2
-    echo "example: $(basename "$0") upstream/main..HEAD" >&2
+    echo "example: $(basename "$0") <merge-base-sha>..HEAD" >&2
     exit 1
 fi