fix(gui): Flatpak Show Results opens the log via host xdg-open

fix(gui): keep Show Results enabled during a run

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

DESIGN.md

@@ -323,6 +323,7 @@ The `testium_assist` editor extension is a thin LSP client that spawns `testium
 Both Flatpak and AppImage export `TESTIUM_VERSION` from a launcher (Flatpak: launcher script in `org.testium.Testium.yaml`; AppImage: `runtime.env` in `AppImageBuilder.yml`). `get_testium_version()` checks `/.flatpak-info` / `APPIMAGE` and reads `TESTIUM_VERSION` rather than relying on package metadata or repo introspection.
 
 ## Recent fixes / notable changes
+- Show Results (GUI): the toolbar action stays enabled during a run (the log grows live, so it is useful mid-test), not just after. In Flatpak `QDesktopServices.openUrl` routes through the OpenURI portal and often opens no editor for a `.log`; `bins.host_open_path()` now spawns `xdg-open` on the host via `flatpak-spawn --host` (returns False outside Flatpak so the caller falls back to `openUrl`).
 - Test-tree search (GUI): a Ctrl+F find bar highlights + navigates matching items, with Name/Type/Doc field checkboxes. Search modifications run under `blockSignals` (else `setBackground`→`itemChanged`→`on_testChecked` storms the controller), and the search/run highlights share one flag-driven `_refresh_highlight()` (run > search > default) so overlapping layers never leave a stale colour. See "## Test-tree search (GUI)".
 - `pytest` item: pytest analogue of `unittest`, but runs on the **host interpreter in a subprocess** (`bins.python_bin()`, like `py_func`) so it works across every packaging channel. A stdlib-only pytest plugin streams collected node-ids + per-test results back over stdout via sentinels; each test becomes a child item with its own PASS/FAIL/SKIP, duration and failure message. Params: `test_file`, `test_method`. Validation item: `test/validation/items/pytest/` (the validation venv now pip-installs `pytest`). See "### `pytest` item".
 - Graceful item load: a self-loading item that fails to load its module/file (e.g. a `unittest` test file importing a missing module, or `pytest` not installed on the host) no longer aborts the **whole** test load. `TestSet._load_item()` wraps the item's `load()`, emits a `tm.print_warn(...)` at load time and records the reason in `item._load_error`; the `@test_run` wrapper turns a non-None `_load_error` into a clean run-time `FAILURE` (message printed once via `write_footer`). The rest of the campaign loads and runs normally. Applies to module-loading items (`unittest`, `pytest`); structural action loading stays fail-fast.