## Summary

I want to simplify our development dependencies a bit.

Fixes #939 

## Problem

tkinter fails with "Can't find a usable init.tcl" on macOS when both:
1. `sys.prefix != sys.base_prefix` (e.g., when using venv, uvx, uv run
--isolated)
2. stdin is a non-TTY device (pytest capture, CI, piped input)

## Root cause

On macOS Aqua, when stdin is non-TTY, Tk's init path
`(Tk_CreateConsoleWindow` -> `TkpInit`) creates a secondary Tcl
interpreter. The existing patch sets `tcl_library` on the main
interpreter, but this secondary interpreter doesn't inherit it and falls
back to compiled-in search paths that don't exist in a relocated/venv
context.

## Fix

Temporarily set the `TCL_LIBRARY` environment variable around the
`Tcl_AppInit` call in `Tkapp_New`. The env var is visible to all
interpreters Tk creates internally during init, then unset immediately
after to avoid environment pollution. Also
extends `_get_tcl_lib_path()` to compute the Tcl library path on Unix
(previously Windows-only).

Patches updated for Python 3.10–3.14.

There might be some more candidates but I think the next goal will be to
use arrays for all the extra args things to avoid needing to use
splitting anywhere, then it should be easy to clean up the rest.

This is like astral-sh/uv#18159 but for PBS.