Fix critical bug: move map declarations before usage

CRITICAL FIX: The script was referencing JOB_VERSION_MAP before declaring
it, which would cause "unbound variable" errors due to set -euo pipefail.

Changes:
- Moved both JOB_MAP and JOB_VERSION_MAP declarations before first usage
- Added helper function get_version_info() to eliminate code duplication
- Replaced 4 repeated linear searches with function calls
- Fixed inconsistent string concatenation (added braces)
- Added documentation comments linking to source of truth files

This improves both correctness and maintainability.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

bin/ci-rerun-failures

@@ -173,21 +173,8 @@ if [ -z "$FAILED_CHECKS" ]; then
   exit 0
 fi
 
-echo -e "${YELLOW}Failed CI jobs:${NC}"
-echo "$FAILED_CHECKS" | while read -r check; do
-  # Try to get version info for the check
-  version_info=""
-  for job_name in "${!JOB_VERSION_MAP[@]}"; do
-    if [[ "$check" == "$job_name"* ]]; then
-      version_info=" (${JOB_VERSION_MAP[$job_name]})"
-      break
-    fi
-  done
-  echo -e "${RED}  ✗ $check${version_info}${NC}"
-done
-echo ""
-
-# Map CI job names to local commands with version info
+# Map CI job names to local commands
+# NOTE: Version numbers below must match .github/workflows/main.yml matrix configuration
 declare -A JOB_MAP
 JOB_MAP["lint-js-and-ruby"]="bundle exec rubocop && yarn run eslint --report-unused-disable-directives && yarn start format.listDifferent"
 JOB_MAP["rspec-package-tests"]="bundle exec rake run_rspec:gem"
@@ -196,11 +183,30 @@ JOB_MAP["dummy-app-integration-tests (3.4, 22, latest)"]="bundle exec rake run_r
 JOB_MAP["dummy-app-integration-tests (3.2, 20, minimum)"]="bundle exec rake run_rspec:all_dummy"
 JOB_MAP["examples"]="bundle exec rake run_rspec:shakapacker_examples"
 
-# Map CI job names to human-readable versions
+# Map CI job names to human-readable versions (matches SWITCHING_CI_CONFIGS.md)
 declare -A JOB_VERSION_MAP
 JOB_VERSION_MAP["dummy-app-integration-tests (3.4, 22, latest)"]="Ruby 3.4, Node 22, Shakapacker 9.3.0, React 19"
 JOB_VERSION_MAP["dummy-app-integration-tests (3.2, 20, minimum)"]="Ruby 3.2, Node 20, Shakapacker 8.2.0, React 18"
 
+# Helper function to get version info for a job name
+get_version_info() {
+  local job_name="$1"
+  for mapped_job_name in "${!JOB_VERSION_MAP[@]}"; do
+    if [[ "$job_name" == "$mapped_job_name"* ]]; then
+      echo " (${JOB_VERSION_MAP[$mapped_job_name]})"
+      return
+    fi
+  done
+  echo ""
+}
+
+echo -e "${YELLOW}Failed CI jobs:${NC}"
+echo "$FAILED_CHECKS" | while read -r check; do
+  version_info=$(get_version_info "$check")
+  echo -e "${RED}  ✗ $check${version_info}${NC}"
+done
+echo ""
+
 # Track what we'll run (deduplicated)
 declare -A COMMANDS_TO_RUN
 
@@ -232,14 +238,7 @@ fi
 echo -e "${BLUE}Will run the following commands:${NC}"
 for cmd in "${!COMMANDS_TO_RUN[@]}"; do
   job_name="${COMMANDS_TO_RUN[$cmd]}"
-  # Try to get version info for the job
-  version_info=""
-  for mapped_job_name in "${!JOB_VERSION_MAP[@]}"; do
-    if [[ "$job_name" == "$mapped_job_name"* ]]; then
-      version_info=" (${JOB_VERSION_MAP[$mapped_job_name]})"
-      break
-    fi
-  done
+  version_info=$(get_version_info "$job_name")
   echo -e "${BLUE}  • $job_name${version_info}:${NC} $cmd"
 done
 echo ""
@@ -273,14 +272,7 @@ FAILED_COMMANDS=()
 
 for cmd in "${!COMMANDS_TO_RUN[@]}"; do
   job_name="${COMMANDS_TO_RUN[$cmd]}"
-  # Try to get version info for the job
-  version_info=""
-  for mapped_job_name in "${!JOB_VERSION_MAP[@]}"; do
-    if [[ "$job_name" == "$mapped_job_name"* ]]; then
-      version_info=" (${JOB_VERSION_MAP[$mapped_job_name]})"
-      break
-    fi
-  done
+  version_info=$(get_version_info "$job_name")
 
   echo -e "${BLUE}▶ Running: $job_name${version_info}${NC}"
   echo -e "${BLUE}Command: $cmd${NC}"
@@ -294,7 +286,7 @@ for cmd in "${!COMMANDS_TO_RUN[@]}"; do
   else
     echo -e "${RED}✗ $job_name${version_info} failed${NC}"
     echo ""
-    FAILED_COMMANDS+=("$job_name$version_info")
+    FAILED_COMMANDS+=("${job_name}${version_info}")
   fi
 done