ci: fetch full git history so setuptools-scm can see tags

actions/checkout@v4 defaults to a shallow, tag-less clone. With no
tags reachable, setuptools-scm falls back to its default base version
(0.1.devN+g<hash>), which fails test_get_superflore_version's sanity
check that the version isn't lower than expected. Reproduced locally:
a --depth 1 clone reads back '0.1.dev1+g<hash>' and fails the test; a
full clone correctly resolves to '0.3.4.devNN+g<hash>' and passes.

Assisted-by: Claude:claude-opus-5
AI-Generated: Uses Claude (claude-opus-5)
Signed-off-by: Rob Woolley <rob.woolley@windriver.com>

Author: robwoolley

.github/workflows/ci.yaml

@@ -16,6 +16,8 @@ jobs:
       runs-on: ${{matrix.os}}
       steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - name: Set up Python ${{matrix.python}}
         uses: actions/setup-python@v5
         with: