feat: add MCP server core, stdio and streamable HTTP transports and serve command

Low-level SDK server built from the catalog plus gitea_api_request, with TOOLSETS/READ_ONLY/DISABLED_TOOLS filters, schema validation without value echo, one audit event per call, static bearer verifier, identity resolver hook, /health, DNS-rebinding protection, rate limiting and fail-closed startup checks.

src/aegis_gitea_mcp/cli.py

@@ -1,16 +1,20 @@
 """Command line entry point (``aegis-gitea-mcp``).
 
-Subcommands: ``serve`` (default), ``setup`` and ``version``. ``serve`` and
-``setup`` are filled in by later chunks.
+Subcommands: ``serve`` (default), ``setup`` and ``version``.
 """
 
 from __future__ import annotations
 
 import argparse
+import os
 import sys
 from collections.abc import Sequence
 
+from pydantic import ValidationError
+
 from aegis_gitea_mcp import __version__, setup_cmd
+from aegis_gitea_mcp.config import Settings, get_settings, reset_settings
+from aegis_gitea_mcp.logging_utils import configure_logging
 
 
 def build_parser() -> argparse.ArgumentParser:
@@ -28,6 +32,15 @@ def build_parser() -> argparse.ArgumentParser:
         default=None,
         help="transport to serve (default: MCP_TRANSPORT, else stdio)",
     )
+    serve.add_argument("--host", default=None, help="HTTP bind address (default: MCP_HOST)")
+    serve.add_argument(
+        "--port",
+        type=int,
+        default=None,
+        choices=range(1, 65536),
+        metavar="PORT",
+        help="HTTP port (default: MCP_PORT)",
+    )
 
     setup = subparsers.add_parser("setup", help="verify a Gitea instance and write the env file")
     setup_cmd.add_arguments(setup)
@@ -35,10 +48,40 @@ def build_parser() -> argparse.ArgumentParser:
     return parser
 
 
-def _not_implemented(command: str) -> int:
-    """Report an unbuilt command and return the usage-error exit code."""
-    print(f"aegis-gitea-mcp {command}: not implemented yet", file=sys.stderr)
-    return 2
+def _load_settings(args: argparse.Namespace) -> Settings | None:
+    """Load settings with the ``serve`` flags applied; print problems and return None."""
+    port = getattr(args, "port", None)
+    overrides = {
+        "MCP_TRANSPORT": getattr(args, "transport", None),
+        "MCP_HOST": getattr(args, "host", None),
+        "MCP_PORT": None if port is None else str(port),
+    }
+    for name, value in overrides.items():
+        if value is not None:
+            os.environ[name] = value
+    reset_settings()
+    try:
+        return get_settings()
+    except ValidationError as exc:
+        # Print field names and messages only: str(exc) would echo the offending values.
+        print("aegis-gitea-mcp: invalid configuration:", file=sys.stderr)
+        for error in exc.errors(include_input=False, include_url=False):
+            field = ".".join(str(part) for part in error["loc"]).upper() or "settings"
+            print(f"  {field}: {error['msg']}", file=sys.stderr)
+        return None
+
+
+def run_serve(args: argparse.Namespace) -> int:
+    """Run the MCP server over the selected transport and return the exit code."""
+    from aegis_gitea_mcp import transports
+
+    settings = _load_settings(args)
+    if settings is None:
+        return 2
+    configure_logging(settings.log_level)
+    if settings.mcp_transport == "http":
+        return transports.run_http(settings)
+    return transports.run_stdio(settings)
 
 
 def main(argv: Sequence[str] | None = None) -> int:
@@ -51,7 +94,7 @@ def main(argv: Sequence[str] | None = None) -> int:
         return 0
     if command == "setup":
         return setup_cmd.run_setup(args)
-    return _not_implemented(command)
+    return run_serve(args)
 
 
 if __name__ == "__main__":  # pragma: no cover