feat: enable Python 3.14 as a required test target

Relax requires-python upper bound (>=3.11,<3.14 -> >=3.11), add the
3.14 trove classifier, and remove continue-on-error from the 3.14
matrix jobs in feature_test.yml so 3.14 failures are now blocking.

The snowfakery dependency was already bumped to >=5.0.0.dev1 in
7310d75; this commit completes the Python 3.14 enablement on top
of that.

3.14 was already present in the CI matrices on dev; only the
continue-on-error gate and requires-python ceiling were holding it
back.

Author: jstvz

.github/workflows/feature_test.yml

@@ -42,7 +42,6 @@ jobs:
     unit_tests:
         name: "Unit tests: ${{ matrix.os }}-${{ matrix.python-version }}"
         runs-on: ${{ matrix.os }}
-        continue-on-error: ${{ matrix.python-version == '3.14' }}
         strategy:
             fail-fast: false
             matrix:
@@ -67,7 +66,6 @@ jobs:
     unit_tests_opt_deps:
         name: "Unit tests with optional dependencies: ${{ matrix.os }}-${{ matrix.python-version }}"
         runs-on: ${{ matrix.os }}
-        continue-on-error: ${{ matrix.python-version == '3.14' }}
         strategy:
             fail-fast: false
             matrix:

pyproject.toml

@@ -7,7 +7,7 @@ name = "cumulusci"
 dynamic = ["readme", "version"]
 description = "Build and release tools for Salesforce developers"
 license = { text = "BSD 3-Clause License" }
-requires-python = ">=3.11,<3.14"
+requires-python = ">=3.11"
 authors = [
     { name = "Salesforce.org", email = "sfdo-mrbelvedere@salesforce.com" },
 ]
@@ -21,6 +21,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 dependencies = [
     "click>=8.2.0",