fix(telegram): add message splitting, timeout, and validation fixes (#246)

High-priority fixes:
- Message length validation and splitting (4096 char limit)
- Empty chat_id validation to prevent silent failures
- Health check timeout (5s) to prevent service hangs

Testing infrastructure:
- Comprehensive test suite (20+ automated tests)
- Quick smoke test script
- Test message generator
- Complete testing documentation

All changes are backward compatible.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

test_helpers/generate_test_messages.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+"""
+Test message generator for Telegram integration testing.
+Generates messages of various lengths for testing message splitting.
+"""
+
+import sys
+
+def generate_short_message():
+    """Generate a short message (< 100 chars)"""
+    return "Hello! This is a short test message."
+
+def generate_medium_message():
+    """Generate a medium message (~ 1000 chars)"""
+    return "This is a medium-length test message. " * 25
+
+def generate_long_message():
+    """Generate a long message (~ 5000 chars, > 4096 limit)"""
+    return "This is a very long test message that will be split into multiple chunks. " * 70
+
+def generate_exact_limit_message():
+    """Generate a message exactly at 4096 char limit"""
+    base = "x" * 4096
+    return base
+
+def generate_over_limit_message():
+    """Generate a message just over the 4096 char limit"""
+    return "x" * 4200
+
+def generate_multi_chunk_message():
+    """Generate a message that requires 3+ chunks"""
+    return "Lorem ipsum dolor sit amet, consectetur adipiscing elit. " * 250
+
+def generate_newline_message():
+    """Generate a message with many newlines (tests newline splitting)"""
+    return "Line of text\n" * 400
+
+def generate_word_boundary_message():
+    """Generate a message with clear word boundaries"""
+    return "word " * 1000
+
+def print_message_info(message, name):
+    """Print information about a message"""
+    print(f"\n{'='*60}")
+    print(f"{name}")
+    print(f"{'='*60}")
+    print(f"Length: {len(message)} characters")
+    print(f"Will split: {'Yes' if len(message) > 4096 else 'No'}")
+    if len(message) > 4096:
+        chunks = (len(message) + 4095) // 4096
+        print(f"Estimated chunks: {chunks}")
+    print(f"{'='*60}")
+    print(message[:200] + "..." if len(message) > 200 else message)
+    print(f"{'='*60}\n")
+
+def main():
+    if len(sys.argv) > 1:
+        test_type = sys.argv[1].lower()
+    else:
+        print("Usage: python3 generate_test_messages.py [type]")
+        print("\nAvailable types:")
+        print("  short      - Short message (< 100 chars)")
+        print("  medium     - Medium message (~1000 chars)")
+        print("  long       - Long message (~5000 chars, requires splitting)")
+        print("  exact      - Exactly 4096 chars")
+        print("  over       - Just over 4096 chars")
+        print("  multi      - Very long (3+ chunks)")
+        print("  newline    - Many newlines (tests line splitting)")
+        print("  word       - Clear word boundaries")
+        print("  all        - Show info for all types")
+        print("\nExample:")
+        print("  python3 generate_test_messages.py long")
+        sys.exit(1)
+
+    messages = {
+        'short': ('Short Message', generate_short_message()),
+        'medium': ('Medium Message', generate_medium_message()),
+        'long': ('Long Message', generate_long_message()),
+        'exact': ('Exact Limit (4096)', generate_exact_limit_message()),
+        'over': ('Just Over Limit', generate_over_limit_message()),
+        'multi': ('Multi-Chunk Message', generate_multi_chunk_message()),
+        'newline': ('Newline Test', generate_newline_message()),
+        'word': ('Word Boundary Test', generate_word_boundary_message()),
+    }
+
+    if test_type == 'all':
+        for name, msg in messages.values():
+            print_message_info(msg, name)
+    elif test_type in messages:
+        name, msg = messages[test_type]
+        # Just print the message for piping to Telegram
+        print(msg)
+    else:
+        print(f"Error: Unknown type '{test_type}'")
+        print("Run without arguments to see available types.")
+        sys.exit(1)
+
+if __name__ == '__main__':
+    main()