collect CLI arguments into a dataclass

Using library "clickdc", collect CLI arguments into a "cli_args"
dataclass.

A small amount of reordering was done, which affects the output of the
helpdoc, but the intention is for this to introduce no other functional
changes.

The properties in "cli_args" are sometimes mutated, for example when
reading comparable values from a DSN.  But mutating the properties is
debatable.

New tests are introduced for the crucial user/host/port/socket
coordinates, but we stop short of adding new tests for every single
CLI argument.

Motivations

 * clarity
 * click_entrypoint() had too many positional arguments
 * adding an CLI argument required adding both a decorator and a
   matching positional argument to click_entrypoint()
 * this work can be a step toward breaking up massive main.py and
   test_main.py

Another related step would be gathering disparate runtime settings into
a self.settings property.

Author: rolandwalker

changelog.md

@@ -1,3 +1,11 @@
+Upcoming (TBD)
+==============
+
+Internal
+---------
+* Collect CLI arguments into a dataclass.
+
+
 1.66.0 (2026/03/21)
 ==============