feat: add psagentai agent with deployment and configuration

Initial project setup including the main agent script, configuration
files, profile JSON state, systemd service unit, startup script,
deployment documentation, and Python dependencies.

Includes .env, venv/, and __pycache__/ which should likely be
excluded via .gitignore to avoid committing secrets and artifacts.

venv/lib/python3.11/site-packages/pip/_internal/resolution/base.py

@@ -0,0 +1,20 @@
+from collections.abc import Callable
+
+from pip._internal.req.req_install import InstallRequirement
+from pip._internal.req.req_set import RequirementSet
+
+InstallRequirementProvider = Callable[
+    [str, InstallRequirement | None], InstallRequirement
+]
+
+
+class BaseResolver:
+    def resolve(
+        self, root_reqs: list[InstallRequirement], check_supported_wheels: bool
+    ) -> RequirementSet:
+        raise NotImplementedError()
+
+    def get_installation_order(
+        self, req_set: RequirementSet
+    ) -> list[InstallRequirement]:
+        raise NotImplementedError()