test: Increase timeout for E2E test to fix macOS CI flakiness

Increased timeout from 5 to 15 seconds for github command E2E test.
The test was flaky on macOS CI due to network latency when
checking non-existent GitHub repos.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_issue_219_e2e.py

@@ -139,7 +139,7 @@ class TestIssue219Problem2CLIFlags(unittest.TestCase):
             ['skill-seekers', 'github', '--repo', 'test/test', '--enhance-local'],
             capture_output=True,
             text=True,
-            timeout=5
+            timeout=15  # Increased timeout for macOS CI environment
         )
 
         # VERIFY: No "unrecognized arguments" error