chore(makefiles): add format-check target and unify formatting logic

- Introduced `format-check` for verification without modification in `llm-gateway` and `knowledge-base` Makefiles.
- Updated `validate` to include `format-check`.
- Added `format-all` to root Makefile for consistent formatting across all components.
- Unexported `VIRTUAL_ENV` to prevent virtual environment warnings.

mcp-servers/llm-gateway/Makefile

@@ -1,4 +1,8 @@
-.PHONY: help install install-dev lint lint-fix format type-check test test-cov validate clean run
+.PHONY: help install install-dev lint lint-fix format format-check type-check test test-cov validate clean run
+
+# Ensure commands in this project don't inherit an external Python virtualenv
+# (prevents uv warnings about mismatched VIRTUAL_ENV when running from repo root)
+unexport VIRTUAL_ENV
 
 # Default target
 help:
@@ -12,6 +16,7 @@ help:
 	@echo "  make lint          - Run Ruff linter"
 	@echo "  make lint-fix      - Run Ruff linter with auto-fix"
 	@echo "  make format        - Format code with Ruff"
+	@echo "  make format-check  - Check if code is formatted"
 	@echo "  make type-check    - Run mypy type checker"
 	@echo ""
 	@echo "Testing:"
@@ -19,7 +24,7 @@ help:
 	@echo "  make test-cov      - Run pytest with coverage"
 	@echo ""
 	@echo "All-in-one:"
-	@echo "  make validate      - Run lint, type-check, and tests"
+	@echo "  make validate      - Run all checks (lint + format + types)"
 	@echo ""
 	@echo "Running:"
 	@echo "  make run           - Run the server locally"
@@ -49,6 +54,10 @@ format:
 	@echo "Formatting code..."
 	@uv run ruff format .
 
+format-check:
+	@echo "Checking code formatting..."
+	@uv run ruff format --check .
+
 type-check:
 	@echo "Running mypy..."
 	@uv run mypy . --ignore-missing-imports
@@ -63,7 +72,7 @@ test-cov:
 	@uv run pytest tests/ -v --cov=. --cov-report=term-missing --cov-report=html
 
 # All-in-one validation
-validate: lint type-check test
+validate: lint format-check type-check
 	@echo "All validations passed!"
 
 # Running