fix(bf-632yt): fix arithmetic operations causing premature script exit

Fixed critical bug where validation script exited prematurely under
set -euo pipefail due to arithmetic operations returning non-zero exit
codes when evaluating to 0.

Changes:
- Replaced ((var++)) with var=$((var + 1))
- Replaced ((var += value)) with var=$((var + value))
- Restructured progress indicator to avoid modulo 0 result

Verification:
- Script now successfully validates all 1,260 corpus files
- Correctly reports 603 valid files with complete license info
- Detects 657 files with missing licenses (expected - PDFium test files)
- Exits with code 1 when validation fails (as designed)

Closes bf-632yt

notes/bf-632yt.md

@@ -47,7 +47,26 @@ Default corpus directory: `tests/fixtures/grep-corpus`
 - ✅ Returns 0 on success, non-zero on validation failure
 - ✅ Outputs summary: total files, total pages, total size, validation status
 
-## Commit
+## Bug Fix (2026-07-05)
 
-- Commit: `c189bfd2`
-- Files changed: `scripts/validate-corpus.sh` (1 file, 114 insertions, 147 deletions)
+Fixed critical issue where script exited prematurely under `set -euo pipefail` due to arithmetic operations returning non-zero exit codes when evaluating to 0.
+
+### Changes made:
+- Replaced all `((var++))` with `var=$((var + 1))`
+- Replaced all `((var += value))` with `var=$((var + value))`
+- Restructured progress indicator to avoid modulo 0 result
+
+### Root cause:
+The `set -e` flag causes scripts to exit when any command returns non-zero. Arithmetic operations like `((x++))` return the result of the expression (0 when x becomes 0 after increment), which triggers `set -e` to exit.
+
+### Verification:
+After fix, script successfully validates all 1,260 files:
+- Total files: 1,260
+- Valid files: 603 (with complete license info)
+- Missing licenses: 657 (expected - PDFium test files)
+- Exit code: 1 (correctly fails when validation errors found)
+
+## Commits
+
+- Initial: `c189bfd2` - Created validation script
+- Fix: `<pending>` - Fixed arithmetic operation exits under set -e

scripts/validate-corpus.sh

@@ -82,14 +82,14 @@ while IFS=',' read -r filename source_url page_count file_size checksum license;
     continue
   fi
 
-  ((total_files++))
+  total_files=$((total_files + 1))
 
   file_path="${CORPUS_SUBDIR}/${filename}"
 
   # Check 1: File existence
   if [[ ! -f "$file_path" ]]; then
     log_error "MISSING: $filename"
-    ((missing_files++))
+    missing_files=$((missing_files + 1))
     continue
   fi
 
@@ -101,7 +101,7 @@ while IFS=',' read -r filename source_url page_count file_size checksum license;
   if [[ "$actual_size" != "$file_size" ]]; then
     log_warn "SIZE MISMATCH: $filename"
     echo "  Expected: $file_size bytes, Got: $actual_size bytes"
-    ((size_mismatches++))
+    size_mismatches=$((size_mismatches + 1))
     continue
   fi
 
@@ -110,26 +110,27 @@ while IFS=',' read -r filename source_url page_count file_size checksum license;
     log_warn "CHECKSUM MISMATCH: $filename"
     echo "  Expected: $checksum"
     echo "  Got:      $actual_checksum"
-    ((checksum_mismatches++))
+    checksum_mismatches=$((checksum_mismatches + 1))
     continue
   fi
 
   # Check 4: License information
   if [[ -z "$license" || "$license" == "null" || "$license" == "unknown" ]]; then
     log_warn "MISSING LICENSE: $filename"
-    ((missing_licenses++))
+    missing_licenses=$((missing_licenses + 1))
     continue
   fi
 
   # All checks passed
-  ((valid_files++))
+  valid_files=$((valid_files + 1))
 
   # Accumulate totals
-  ((total_pages += page_count))
-  ((total_size += file_size))
+  total_pages=$((total_pages + page_count))
+  total_size=$((total_size + file_size))
 
   # Progress indicator
-  if [[ $((valid_files % 200)) -eq 0 && $valid_files -gt 0 ]]; then
+  remainder=$((valid_files % 200))
+  if [[ $valid_files -gt 0 ]] && [[ $remainder -eq 0 ]]; then
     log_info "Validated $valid_files files..."
   fi