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>

quick_test.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+# Quick smoke test for Telegram integration
+# Run this before committing code changes
+
+set -e
+
+echo "🔥 Quick Telegram Smoke Test"
+echo ""
+
+# Test 1: Compile check
+echo -n "1. Compiling... "
+cargo build --release --quiet 2>&1 && echo "✓" || { echo "✗ FAILED"; exit 1; }
+
+# Test 2: Unit tests
+echo -n "2. Running tests... "
+cargo test telegram_split --lib --quiet 2>&1 && echo "✓" || { echo "✗ FAILED"; exit 1; }
+
+# Test 3: Health check
+echo -n "3. Health check... "
+timeout 7 target/release/zeroclaw channel doctor &>/dev/null && echo "✓" || echo "⚠ (configure bot first)"
+
+# Test 4: File checks
+echo -n "4. Code structure... "
+grep -q "TELEGRAM_MAX_MESSAGE_LENGTH" src/channels/telegram.rs && \
+grep -q "split_message_for_telegram" src/channels/telegram.rs && \
+grep -q "tokio::time::timeout" src/channels/telegram.rs && \
+echo "✓" || { echo "✗ FAILED"; exit 1; }
+
+echo ""
+echo "✅ Quick tests passed! Run ./test_telegram_integration.sh for full suite."