fix(grading): stop autograder from silently crashing under bash 5

`((score += l1))`-style compound assignment is a false command in bash
whenever the resulting value is 0 -- exit status 1 even though the
assignment succeeded. Under `set -e` (used by every autograder here),
that silently kills the script mid-run on GitHub Actions' Ubuntu
runners (bash 5), while working fine locally on macOS (bash 3.2, which
does not enforce this). Any student whose running score hits exactly 0
at a checkpoint -- most commonly an early, mostly-empty submission --
got a grading run that failed with a bare "exit code 1" and no
score.json update, not a real 0 score.

Reproduced locally with bash 5 against an empty scaffold; confirmed
exit 0 after the fix, and re-verified real solution runs still score
correctly. Fix: rewrite every `((var += expr))`/`((var -= expr))` as
`var=$((var + expr))`, and guard bare check_*() calls that can
legitimately return non-zero (a warn/fail signal, not a script error)
with `|| true` so `set -e` does not treat them as fatal.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: Lasse Benninga

.hyf/test.sh

@@ -20,24 +20,24 @@ warn() { _grader_details+=("WARN: $1"); }
 l1=0
 for f in Dockerfile "src/pipeline.py" "tests/test_pipeline.py" "AI_ASSIST.md"; do
   if [[ -f "$REPO_ROOT/$f" ]]; then
-    ((l1 += 3))
+    l1=$((l1 + 3))
   else
     fail "missing $f"
   fi
 done
 # ci.yml
 if ls "$REPO_ROOT/.github/workflows/"*.yml 2>/dev/null | grep -q .; then
-  ((l1 += 2))
+  l1=$((l1 + 2))
 else
   fail "missing .github/workflows/*.yml"
 fi
 # requirements.txt or pyproject.toml
 if [[ -f "$REPO_ROOT/requirements.txt" ]] || [[ -f "$REPO_ROOT/pyproject.toml" ]]; then
-  ((l1 += 1))
+  l1=$((l1 + 1))
 else
   fail "missing requirements.txt or pyproject.toml"
 fi
-((score += l1))
+score=$((score + l1))
 pass "Level 1: required files ($l1/15 pts)"
 
 
@@ -46,7 +46,7 @@ l2=0
 df="$REPO_ROOT/Dockerfile"
 if [[ -f "$df" ]]; then
   if grep -qE "^FROM\s+python:3\.11-slim" "$df"; then
-    ((l2 += 5)); pass "Dockerfile uses python:3.11-slim base image"
+    l2=$((l2 + 5)); pass "Dockerfile uses python:3.11-slim base image"
   else
     fail "Dockerfile does not use python:3.11-slim base image"
   fi
@@ -55,18 +55,18 @@ if [[ -f "$df" ]]; then
   req_line=$(grep -n "COPY.*requirements" "$df" | head -1 | cut -d: -f1 || echo 0)
   src_line=$(grep -n "COPY.*src" "$df" | head -1 | cut -d: -f1 || echo 9999)
   if [[ "$req_line" -gt 0 && "$src_line" -lt 9999 && "$req_line" -lt "$src_line" ]]; then
-    ((l2 += 7)); pass "Dockerfile copies requirements before source (cache-friendly)"
+    l2=$((l2 + 7)); pass "Dockerfile copies requirements before source (cache-friendly)"
   else
     fail "Dockerfile does not copy requirements before source code"
   fi
 
   if grep -qE "^CMD" "$df"; then
-    ((l2 += 3)); pass "Dockerfile has a CMD instruction"
+    l2=$((l2 + 3)); pass "Dockerfile has a CMD instruction"
   else
     fail "Dockerfile missing CMD instruction"
   fi
 fi
-((score += l2))
+score=$((score + l2))
 pass "Level 2: Dockerfile ($l2/15 pts)"
 
 # ── Level 3 (10 pts): unit tests ─────────────────────────────────────────────
@@ -75,67 +75,67 @@ test_file="$REPO_ROOT/tests/test_pipeline.py"
 if [[ -f "$test_file" ]]; then
   test_count=$(grep -cE "^[[:space:]]*def test_" "$test_file" || true)
   if [[ "$test_count" -ge 2 ]]; then
-    ((l3 += 7)); pass "tests/test_pipeline.py has $test_count test functions (≥2 required)"
+    l3=$((l3 + 7)); pass "tests/test_pipeline.py has $test_count test functions (≥2 required)"
   else
     fail "tests/test_pipeline.py has only $test_count test function(s) — at least 2 required"
   fi
   if ! grep -q "NotImplementedError" "$test_file"; then
-    ((l3 += 3)); pass "tests/test_pipeline.py has no NotImplementedError stubs remaining"
+    l3=$((l3 + 3)); pass "tests/test_pipeline.py has no NotImplementedError stubs remaining"
   else
     fail "tests/test_pipeline.py still contains NotImplementedError stubs"
   fi
 fi
-((score += l3))
+score=$((score + l3))
 pass "Level 3: unit tests ($l3/10 pts)"
 
 # ── Level 4 (10 pts): pinned dependencies ───────────────────────────────────
 l4=0
 if [[ -f "$REPO_ROOT/requirements.txt" ]]; then
   pinned=$(grep -cE "^[a-zA-Z].*==" "$REPO_ROOT/requirements.txt" || true)
   if [[ "$pinned" -ge 1 ]]; then
-    ((l4 += 7)); pass "requirements.txt has $pinned pinned package(s)"
+    l4=$((l4 + 7)); pass "requirements.txt has $pinned pinned package(s)"
   else
     fail "requirements.txt has no pinned packages (use package==version)"
   fi
 fi
 if [[ -f "$REPO_ROOT/uv.lock" ]]; then
-  ((l4 += 3)); pass "uv.lock present (full dependency tree pinned)"
+  l4=$((l4 + 3)); pass "uv.lock present (full dependency tree pinned)"
 elif [[ "$l4" -ge 7 ]]; then
-  ((l4 += 3)); pass "requirements.txt pins satisfied (no uv.lock needed)"
+  l4=$((l4 + 3)); pass "requirements.txt pins satisfied (no uv.lock needed)"
 fi
-((score += l4))
+score=$((score + l4))
 pass "Level 4: pinned dependencies ($l4/10 pts)"
 
 # ── Level 5 (20 pts): CI workflow ────────────────────────────────────────────
 l5=0
 ci_file=$(ls "$REPO_ROOT/.github/workflows/"*.yml 2>/dev/null | head -1 || true)
 if [[ -n "$ci_file" ]]; then
-  grep -q "pull_request" "$ci_file" && { ((l5 += 4)); pass "ci.yml triggers on pull_request"; } || fail "ci.yml missing pull_request trigger"
-  grep -qE '\bmain\b' "$ci_file" && { ((l5 += 4)); pass "ci.yml triggers on push to main"; } || fail "ci.yml missing push to main trigger"
-  grep -q "ruff check" "$ci_file" && { ((l5 += 3)); pass "ci.yml runs ruff check (lint)"; } || fail "ci.yml missing ruff check step"
-  grep -q "ruff format" "$ci_file" && { ((l5 += 3)); pass "ci.yml runs ruff format (format check)"; } || fail "ci.yml missing ruff format step"
-  grep -q "pytest" "$ci_file" && { ((l5 += 3)); pass "ci.yml runs pytest"; } || fail "ci.yml missing pytest step"
-  grep -q "docker build" "$ci_file" && { ((l5 += 3)); pass "ci.yml runs docker build"; } || fail "ci.yml missing docker build step"
+  grep -q "pull_request" "$ci_file" && { l5=$((l5 + 4)); pass "ci.yml triggers on pull_request"; } || fail "ci.yml missing pull_request trigger"
+  grep -qE '\bmain\b' "$ci_file" && { l5=$((l5 + 4)); pass "ci.yml triggers on push to main"; } || fail "ci.yml missing push to main trigger"
+  grep -q "ruff check" "$ci_file" && { l5=$((l5 + 3)); pass "ci.yml runs ruff check (lint)"; } || fail "ci.yml missing ruff check step"
+  grep -q "ruff format" "$ci_file" && { l5=$((l5 + 3)); pass "ci.yml runs ruff format (format check)"; } || fail "ci.yml missing ruff format step"
+  grep -q "pytest" "$ci_file" && { l5=$((l5 + 3)); pass "ci.yml runs pytest"; } || fail "ci.yml missing pytest step"
+  grep -q "docker build" "$ci_file" && { l5=$((l5 + 3)); pass "ci.yml runs docker build"; } || fail "ci.yml missing docker build step"
 fi
-((score += l5))
+score=$((score + l5))
 pass "Level 5: CI workflow ($l5/20 pts)"
 
 # ── Level 6 (15 pts): env-var configuration ──────────────────────────────────
 l6=0
 py="$REPO_ROOT/src/pipeline.py"
 if [[ -f "$py" ]]; then
   if grep -qE "os\.(environ|getenv)|from os import (environ|getenv)" "$py"; then
-    ((l6 += 10)); pass "pipeline.py reads config from os.environ/os.getenv"
+    l6=$((l6 + 10)); pass "pipeline.py reads config from os.environ/os.getenv"
   else
     fail "pipeline.py does not read from os.environ or os.getenv"
   fi
   if ! grep -q "NotImplementedError" "$py"; then
-    ((l6 += 5)); pass "pipeline.py has no NotImplementedError stubs remaining"
+    l6=$((l6 + 5)); pass "pipeline.py has no NotImplementedError stubs remaining"
   else
     fail "pipeline.py still contains NotImplementedError"
   fi
 fi
-((score += l6))
+score=$((score + l6))
 pass "Level 6: env-var config ($l6/15 pts)"
 
 # ── Level 7 (10 pts): ACR screenshot ────────────────────────────────────────
@@ -144,14 +144,14 @@ screenshot="$REPO_ROOT/assets/acr_push_week5.png"
 if [[ -f "$screenshot" ]]; then
   size=$(wc -c < "$screenshot")
   if [[ "$size" -gt 1024 ]]; then
-    ((l7 += 10)); pass "assets/acr_push_week5.png present and non-trivial (${size} bytes)"
+    l7=$((l7 + 10)); pass "assets/acr_push_week5.png present and non-trivial (${size} bytes)"
   else
     fail "assets/acr_push_week5.png exists but looks empty (${size} bytes)"
   fi
 else
   fail "assets/acr_push_week5.png missing (Task 7 deliverable)"
 fi
-((score += l7))
+score=$((score + l7))
 pass "Level 7: ACR screenshot ($l7/10 pts)"
 
 # ── Level 8 (5 pts): AI_ASSIST.md content ───────────────────────────────────
@@ -165,22 +165,22 @@ if [[ -f "$ai" ]]; then
   has_todo=$(grep -c "^TODO:" "$ai" || true)
 
   if [[ "$has_prompt" -ge 1 && "$has_code" -ge 1 && "$has_changed" -ge 1 ]]; then
-    ((l8 += 3)); pass "AI_ASSIST.md has all three required sections"
+    l8=$((l8 + 3)); pass "AI_ASSIST.md has all three required sections"
   else
     fail "AI_ASSIST.md missing one or more required sections"
   fi
   if [[ "$chars" -gt 500 && "$has_todo" -eq 0 ]]; then
-    ((l8 += 2)); pass "AI_ASSIST.md is filled in (${chars} chars, no TODO placeholders)"
+    l8=$((l8 + 2)); pass "AI_ASSIST.md is filled in (${chars} chars, no TODO placeholders)"
   else
     fail "AI_ASSIST.md still contains TODO placeholders or is too short (${chars} chars)"
   fi
 fi
-((score += l8))
+score=$((score + l8))
 pass "Level 8: AI report ($l8/5 pts)"
 
 # ── Code hygiene (warnings from grader_lib) ──────────────────────────────────
-check_no_print_statements "$REPO_ROOT/src" "src/"
-check_gitignore_python "$REPO_ROOT/.gitignore"
+check_no_print_statements "$REPO_ROOT/src" "src/" || true
+check_gitignore_python "$REPO_ROOT/.gitignore" || true
 
 # ── Final result ─────────────────────────────────────────────────────────────
 passing_score=60