CI: split OS-specific addon tests via filename convention

The Windows unit-test job hung on TMGimporter's DB-backed tests because
make_database("sqlite").load(":memory:", None) deadlocks under the
conda-forge GTK + pip Gramps combination. Rather than patch the hang,
introduce a filename convention so per-addon authors can declare OS
scope up front:

  test_*.py              general (every OS)
  test_linux_*.py        Linux-only
  test_windows_*.py      Windows-only
  test_integration_*.py  Linux-only, full-pipeline/DB-backed (pre-existing)

unit-test-linux skips test_windows_* and test_integration_*;
unit-test-windows skips test_linux_* and test_integration_*.

Applied to TMGimporter: the 13 DB-backed classes in tests/test_libtmg.py
move to tests/test_linux_libtmg.py (along with the _Rec/_table/_make_db/
_add_person/_MockUser helpers they use). The 7 pure-logic classes
(TestStripTmgCodes, TestTmgDateToGrampsDate, TestNumTo{Month,Date},
TestParseDate, TestRepoTypeFromName, TestUrlFromName) stay in
test_libtmg.py and will run on every OS.

Locally all 175 tests still pass via run-addon-unit.sh TMGimporter.

Author: eduralph

.github/workflows/ci.yml

@@ -139,6 +139,14 @@ jobs:
           fi
 
       - name: Run per-addon unit tests
+        # Filename convention (all OSes):
+        #   test_*.py              — general (any OS)
+        #   test_linux_*.py        — Linux-only
+        #   test_windows_*.py      — Windows-only
+        #   test_integration_*.py  — Linux-only, full-pipeline/DB-backed
+        # The Linux job runs test_*.py except the Windows-only and
+        # integration buckets. Integration tests run in their own job.
+        #
         # shell: bash — the container's default shell is /bin/sh
         # (dash on python:3.12-slim), which does not support the
         # ${var//pattern/repl} and ${var%.py} parameter expansions
@@ -152,6 +160,7 @@ jobs:
             [ -f "$f" ] || continue
             case "$(basename "$f")" in
               test_integration*) continue ;;
+              test_windows_*)    continue ;;
             esac
             case "$f" in
               Sqlite/tests/test_sqlite.py) continue ;;
@@ -226,6 +235,8 @@ jobs:
           fi
 
       - name: Run per-addon unit tests
+        # See filename-convention note in unit-test-linux. The Windows
+        # job runs test_*.py except test_linux_* and test_integration_*.
         env:
           PYTHONPATH: .
         run: |
@@ -234,6 +245,7 @@ jobs:
             [ -f "$f" ] || continue
             case "$(basename "$f")" in
               test_integration*) continue ;;
+              test_linux_*)      continue ;;
             esac
             case "$f" in
               Sqlite/tests/test_sqlite.py) continue ;;