Create separate tox environments for py314 and py314t

Instead of mapping both 3.14 and 3.14t to the same py314 environment,
create separate environments:
- py314 for regular Python 3.14
- py314t for free-threading Python 3.14t

This resolves the "env name py314 conflicting with base python" error
by allowing tox to automatically detect the correct Python interpreter
for each build type. Tox recognizes environment names ending with 't'
as free-threaded Python implementations.

Author: theskumar

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = lint,py{310,311,312,313,314},pypy3,manifest,coverage-report
+envlist = lint,py{310,311,312,313,314,314t},pypy3,manifest,coverage-report
 
 [gh-actions]
 python =
@@ -8,7 +8,7 @@ python =
     3.12: py312
     3.13: py313, lint, manifest
     3.14: py314
-    3.14t: py314
+    3.14t: py314t
     pypy-3.11: pypy3
 
 [testenv]
@@ -17,14 +17,11 @@ deps =
     pytest-cov
     sh >= 2.0.2, <3
     click
-    py{310,311,312,313,314,pypy3}: ipython
+    py{310,311,312,313,314,314t,pypy3}: ipython
 commands = pytest --cov --cov-report=term-missing {posargs}
 depends =
-    py{310,311,312,313,314},pypy3: coverage-clean
-    coverage-report: py{310,311,312,313,314},pypy3
-
-[testenv:py314]
-basepython = python3
+    py{310,311,312,313,314,314t},pypy3: coverage-clean
+    coverage-report: py{310,311,312,313,314,314t},pypy3
 
 [testenv:lint]
 skip_install = true