feat(scripts): add local Codex security review runner

bin/.shellcheck-0.11.0.pkg

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+hermit

bin/.yq-4.53.3.pkg

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+hermit

bin/shellcheck

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+.shellcheck-0.11.0.pkg

bin/yq

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+.yq-4.53.3.pkg

scripts/codex-security-review-local.sh

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+#!/usr/bin/env bash
+# Run the Codex Security Review locally, reusing the prompt/model from the CI workflow.
+# Usage: scripts/codex-security-review-local.sh [base-ref]  (default: origin/main)
+# shellcheck disable=SC2016 # single-quoted ${{ env.* }} are literal workflow tokens, not expansions
+set -euo pipefail
+
+REPO_ROOT=$(git rev-parse --show-toplevel)
+cd "$REPO_ROOT"
+
+WORKFLOW_FILE=.github/workflows/codex-security-review.yml
+BASE_REF=${1:-origin/main}
+
+if ! command -v yq >/dev/null 2>&1; then
+  echo "yq not found on PATH. Activate hermit first: . ./bin/activate-hermit" >&2
+  exit 1
+fi
+
+# codex must be an externally installed binary: anything under the reviewed
+# checkout (Hermit shims in bin/, a branch-added PATH entry) is attacker code
+# when reviewing an untrusted branch, and codex runs with the developer's login.
+CODEX_BIN=$(command -v codex || true)
+if [ -z "$CODEX_BIN" ]; then
+  echo "codex CLI not found. Install with: brew install codex (then: codex login)" >&2
+  exit 1
+fi
+case "$(cd "$(dirname "$CODEX_BIN")" && pwd -P)/" in
+  "$REPO_ROOT"/*)
+    echo "Refusing to run $CODEX_BIN: it resolves inside the reviewed checkout." >&2
+    echo "Install codex outside the repository (brew install codex) so a malicious branch cannot substitute it." >&2
+    exit 1
+    ;;
+esac
+
+MERGE_BASE=$(git merge-base "$BASE_REF" HEAD)
+HEAD_SHA=$(git rev-parse HEAD)
+
+MODEL=$(yq '.jobs.security-review.env.CODEX_MODEL // ""' "$WORKFLOW_FILE")
+EFFORT=$(yq '.jobs.security-review.env.CODEX_REASONING_EFFORT // ""' "$WORKFLOW_FILE")
+if [ -z "$MODEL" ] || [ -z "$EFFORT" ]; then
+  echo "Could not read CODEX_MODEL / CODEX_REASONING_EFFORT from $WORKFLOW_FILE" >&2
+  exit 1
+fi
+
+# CI reviews base...head; locally we also include uncommitted tracked changes.
+REVIEW_DIFF_FILE=.git/codex-review.diff
+git diff --find-renames --submodule=diff --unified=40 "$MERGE_BASE" > "$REVIEW_DIFF_FILE"
+if [ ! -s "$REVIEW_DIFF_FILE" ]; then
+  echo "No changes found between $BASE_REF ($MERGE_BASE) and the working tree." >&2
+  exit 1
+fi
+
+ORIGIN_URL=$(git remote get-url origin)
+REPO_SLUG=$(echo "$ORIGIN_URL" | sed -E 's#(git@[^:]+:|https://[^/]+/)##; s#\.git$##')
+
+# Honest provenance: with a dirty tree the diff contains content no commit has,
+# so the prompt must not claim a HEAD pin nor link findings to HEAD blobs.
+if git diff --quiet HEAD --; then
+  REVIEW_SCOPE_SHA=$HEAD_SHA
+  REVIEW_RANGE="$MERGE_BASE...$HEAD_SHA"
+  REVIEW_BLOB_BASE="https://github.com/$REPO_SLUG/blob/$HEAD_SHA"
+else
+  REVIEW_SCOPE_SHA="$HEAD_SHA plus uncommitted working-tree changes"
+  REVIEW_RANGE="$MERGE_BASE...working-tree"
+  REVIEW_BLOB_BASE="file://$REPO_ROOT"
+fi
+
+# yq resolves the `prompt: |` block scalar natively (no indent arithmetic).
+PROMPT=$(yq '.jobs.security-review.steps[] | select(.id == "run_codex") | .with.prompt // ""' "$WORKFLOW_FILE")
+if [ -z "$PROMPT" ]; then
+  echo "Could not read the run_codex prompt from $WORKFLOW_FILE" >&2
+  exit 1
+fi
+
+# Fill in the ${{ env.* }} refs CI would substitute.
+PROMPT=${PROMPT//'${{ env.REVIEW_DIFF_FILE }}'/$REVIEW_DIFF_FILE}
+PROMPT=${PROMPT//'${{ env.REVIEW_HEAD_SHA }}'/$REVIEW_SCOPE_SHA}
+PROMPT=${PROMPT//'${{ env.REVIEW_COMMIT_RANGE }}'/$REVIEW_RANGE}
+PROMPT=${PROMPT//'${{ env.REVIEW_BLOB_BASE_URL }}'/$REVIEW_BLOB_BASE}
+if [[ "$PROMPT" == *'${{'* ]]; then
+  echo "Prompt references an unhandled \${{ ... }} expression; update this script's substitutions for $WORKFLOW_FILE" >&2
+  exit 1
+fi
+
+echo "Running Codex Security Review (model=$MODEL, effort=$EFFORT) on $(wc -l < "$REVIEW_DIFF_FILE" | tr -d ' ') diff lines..."
+
+LAST_MSG_FILE=.git/codex-review-last-message.txt
+"$CODEX_BIN" exec \
+  --sandbox read-only \
+  --model "$MODEL" \
+  -c "model_reasoning_effort=$EFFORT" \
+  --output-last-message "$LAST_MSG_FILE" \
+  "$PROMPT"
+
+# Same validation as CI, then render review_markdown for terminal reading.
+RESULT_JSON=.git/codex-review-result.json
+sed -e '1{/^```/d;}' -e '${/^[[:space:]]*```[[:space:]]*$/d;}' "$LAST_MSG_FILE" > "$RESULT_JSON"
+
+RISK=$(yq -p=json -oy '.overall_risk // ""' "$RESULT_JSON")
+case "$RISK" in
+  CRITICAL|HIGH|MEDIUM|LOW|NONE) ;;
+  *) echo "Invalid overall_risk: '$RISK'" >&2; exit 1 ;;
+esac
+if [ "$(yq -p=json -oy '.review_markdown | type' "$RESULT_JSON")" != "!!str" ]; then
+  echo "review_markdown must be a string" >&2
+  exit 1
+fi
+
+REVIEW_MD=$(yq -p=json -oy '.review_markdown' "$RESULT_JSON")
+if [ -z "$REVIEW_MD" ]; then
+  echo "review_markdown must be a non-empty string" >&2
+  exit 1
+fi
+
+printf '\nOverall risk: %s\n\n' "$RISK"
+printf '%s\n' "$REVIEW_MD"