feat(examples): add code-review checker scripts, rule docs, and diff fixtures

Author: DNKYr

examples/skills_code_review_agent/fixtures/async_leak.diff

@@ -0,0 +1,14 @@
+--- a/app/worker.py
++++ b/app/worker.py
+@@ -5,6 +5,9 @@ async def start():
+     config = load_config()
++    session = aiohttp.ClientSession()
++    asyncio.create_task(poll_updates())
++    f = open("data.txt")
+     return config
+--- a/tests/test_worker.py
++++ b/tests/test_worker.py
+@@ -1,2 +1,3 @@
+ def test_start():
++    assert True
+     pass

examples/skills_code_review_agent/fixtures/db_lifecycle.diff

@@ -0,0 +1,15 @@
+--- a/app/repository.py
++++ b/app/repository.py
+@@ -8,6 +8,10 @@ def reset_balances():
+     logger.info("resetting balances")
++    conn = sqlite3.connect("app.db")
++    cur = conn.cursor()
++    cur.execute("UPDATE accounts SET balance = 0")
++    conn.commit()
+     return True
+--- a/tests/test_repository.py
++++ b/tests/test_repository.py
+@@ -1,2 +1,3 @@
+ def test_reset():
++    assert True
+     pass

examples/skills_code_review_agent/fixtures/duplicate_finding.diff

@@ -0,0 +1,12 @@
+--- a/app/dynamic.py
++++ b/app/dynamic.py
+@@ -3,5 +3,6 @@ def run_snippet(snippet, use_eval):
+     logger.debug("running snippet")
++    result = eval(snippet) if use_eval else exec(snippet)
+     return result
+--- a/tests/test_dynamic.py
++++ b/tests/test_dynamic.py
+@@ -1,2 +1,3 @@
+ def test_run():
++    assert True
+     pass

examples/skills_code_review_agent/fixtures/missing_test.diff

@@ -0,0 +1,8 @@
+--- a/app/service.py
++++ b/app/service.py
+@@ -5,6 +5,9 @@ def process(order):
+     validate(order)
++    if order.total < 0:
++        raise ValueError("negative total")
++    order.status = "processed"
+     return order

examples/skills_code_review_agent/fixtures/sandbox_failure.diff

@@ -0,0 +1,12 @@
+--- a/app/misc.py
++++ b/app/misc.py
+@@ -1,3 +1,4 @@
+ def greet(name):
++    # trivial change used by the sandbox-failure scenario
+     return "hello " + name
+--- a/tests/test_misc.py
++++ b/tests/test_misc.py
+@@ -1,2 +1,3 @@
+ def test_greet():
++    assert True
+     pass

examples/skills_code_review_agent/fixtures/secret_leak.diff

@@ -0,0 +1,14 @@
+--- a/app/settings.py
++++ b/app/settings.py
+@@ -1,4 +1,7 @@
+ APP_NAME = "demo"
++API_KEY = "sk-fakefakefakefakefakefake123456"
++DB_PASSWORD = "prod-db-pass-2026"
++aws_key = "AKIA0123456789ABCDEF"
+ DEBUG = False
+--- a/tests/test_settings.py
++++ b/tests/test_settings.py
+@@ -1,2 +1,3 @@
+ def test_settings():
++    assert True
+     pass

examples/skills_code_review_agent/fixtures/security_eval.diff

@@ -0,0 +1,14 @@
+--- a/app/handler.py
++++ b/app/handler.py
+@@ -10,6 +10,9 @@ def handle(request):
+     data = request.get("data", "")
++    result = eval(data)
++    subprocess.run(cmd, shell=True)
++    row = cursor.execute(f"SELECT * FROM users WHERE name = '{name}'")
+     return result
+--- a/tests/test_handler.py
++++ b/tests/test_handler.py
+@@ -1,2 +1,3 @@
+ def test_handle():
++    assert True
+     pass

examples/skills_code_review_agent/skills/code-review/references/rules/async_resource_leak.md

@@ -0,0 +1,22 @@
+# Async Resource Leak Rule
+
+Detects resource management issues in async Python code.
+
+## Patterns
+
+| Pattern | Severity | Confidence | Guidance |
+|---------|----------|------------|----------|
+| `aiohttp.ClientSession()` without `async with` | high | 0.8 | Use `async with aiohttp.ClientSession() as session:` or ensure session.close() is awaited. |
+| `asyncio.create_task()` without storing reference | medium | 0.7 | Store the task and await/cancel it; unreferenced tasks may be garbage collected mid-flight. |
+| `open()` assigned without `with` context manager | medium | 0.7 | Use `with open(...) as f:` so the handle is always closed. |
+
+## Rationale
+
+Resources created inside async functions must be properly managed. Leaked sessions,
+fire-and-forget tasks, and unclosed file handles can cause connection pool exhaustion,
+memory leaks, and unpredictable behavior under load.
+
+## Remediation
+
+Wrap resources in context managers (`async with` / `with`) or ensure explicit cleanup
+in `finally` blocks.

examples/skills_code_review_agent/skills/code-review/references/rules/db_lifecycle.md

@@ -0,0 +1,22 @@
+# Database Lifecycle Rule
+
+Detects database connections, cursors, and transactions opened without proper lifecycle management.
+
+## Patterns
+
+| Pattern | Severity | Confidence | Guidance |
+|---------|----------|------------|----------|
+| `.connect()` without context manager or close() | high | 0.8 | Use `with ...connect(...) as conn:` or close the connection in a finally block. |
+| `.cursor()` without context manager | low | 0.5 | Close the cursor or use a context manager. |
+| `.commit()` without rollback handling | medium | 0.65 | Wrap the transaction in try/except and roll back on failure. |
+
+## Rationale
+
+Unclosed database connections leak file descriptors and connection pool slots.
+Transactions committed without rollback handling can leave data in an inconsistent
+state on error.
+
+## Remediation
+
+- Use context managers (`with conn:` / `with conn.cursor()`) wherever possible.
+- Always wrap transactions in `try/except` and call `rollback()` on failure.

examples/skills_code_review_agent/skills/code-review/references/rules/missing_test.md

@@ -0,0 +1,24 @@
+# Missing Test Rule
+
+Detects source code changes that lack corresponding test file changes.
+
+## Trigger
+
+Fires when a diff contains added lines in `.py` source files but no changes in:
+- Files under `tests/` directories
+- Files whose name starts with `test_` or ends with `_test.py`
+
+## Findings
+
+| Condition | Severity | Confidence | Guidance |
+|-----------|----------|------------|----------|
+| Source .py changed, no test files touched | medium | 0.8 | Add or update unit tests covering the changed behavior. |
+
+## Rationale
+
+Every behavior change should include or reference a test. Without test coverage,
+regressions go undetected.
+
+## Remediation
+
+Add or update unit tests that exercise the changed code paths.