feat(test): add developer test-quick command

Add scripts/test-quick.sh and Makefile with:
- test-quick: runs ruff check + unit tests + smoke tests
- No real provider keys or platform accounts required
- Suitable for local branch self-test

Update tests/README.md:
- Document test-quick command
- Document test factories package
- Add smoke tests and factories directory structure

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/test-quick.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Quick developer self-test command
+# Runs linting, unit tests, and smoke tests without requiring real provider keys
+# Suitable for local branch validation
+
+set -e
+
+echo "=== LangBot Quick Self-Test ==="
+echo ""
+
+# 1. Ruff check
+echo "[1/3] Running ruff check..."
+if command -v ruff &> /dev/null; then
+    ruff check src/langbot/ tests/ --quiet || {
+        echo "⚠ Ruff check found issues. Run 'ruff check --fix' to auto-fix."
+    }
+else
+    echo "⚠ ruff not installed, skipping lint check"
+fi
+echo ""
+
+# 2. Unit tests
+echo "[2/3] Running unit tests..."
+uv run pytest tests/unit_tests/ -q --tb=short 2>&1 | tail -5
+echo ""
+
+# 3. Smoke tests (if exists)
+echo "[3/3] Running smoke tests..."
+if [ -d "tests/smoke" ]; then
+    uv run pytest tests/smoke/ -q --tb=short 2>&1 | tail -5
+else
+    echo "No smoke tests found, skipping"
+fi
+echo ""
+
+echo "=== Quick Self-Test Complete ==="