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/lxml/includes/dtdvalid.pxd

@@ -0,0 +1,18 @@
+from lxml.includes cimport tree
+from lxml.includes.tree cimport xmlDoc, xmlDtd
+
+cdef extern from "libxml/valid.h" nogil:
+    ctypedef void (*xmlValidityErrorFunc)(void * ctx, const char * msg, ...) noexcept
+    ctypedef void (*xmlValidityWarningFunc)(void * ctx, const char * msg, ...) noexcept
+
+    ctypedef struct xmlValidCtxt:
+        void *userData
+        xmlValidityErrorFunc error
+        xmlValidityWarningFunc warning
+
+    cdef xmlValidCtxt* xmlNewValidCtxt()
+    cdef void xmlFreeValidCtxt(xmlValidCtxt* cur)
+
+    cdef int xmlValidateDtd(xmlValidCtxt* ctxt, xmlDoc* doc, xmlDtd* dtd)
+    cdef tree.xmlElement* xmlGetDtdElementDesc(
+        xmlDtd* dtd, tree.const_xmlChar* name)