GUI: Config validation errors handler dialog & layout fixes - #3397

Refactors project loading in the main GUI window to consistently validate config files and recover from failures. It adds a structured error dialog with Retry/Edit/Cancel actions, opens the config editor for repair, and reloads after edits. The flow now routes recent-project opens through the same validation path, clears partial tabs before retrying, and updates project state/load methods to return success status so invalid or unreadable configs no longer leave stale UI state.

Refines `SelectedShuffleDisplay` error rendering when `pose_cfg.yaml` is missing by formatting the message with line breaks and full path visibility. The label is now configured for plain text, word wrapping, expandable sizing, and mouse/keyboard text selection, making long file paths easier to read and copy.

Move window sizing constants to module scope and stop forcing the main window max size to screen dimensions. This allows the maximize button to work properly while preserving the initial resize factor and minimum window size defaults.

Wrap `DefaultTab`’s main content in a `QScrollArea` with a dedicated content widget and zero outer margins so long tab content can be scrolled instead of being clipped. Also updates the `parent` type hint to `QtWidgets.QWidget | None` for consistency with modern typing style.

Update `VideoSelectionWidget` so the selected-videos status label can wrap text and expand horizontally. This improves readability when many videos are selected and prevents the text from being clipped in the GUI layout.

* squashed updates for GUI config validation error handling

* replace getattr guard with explicit attr

- Initialize self._config_monitor = None early in __init__
- Replace getattr(self, "_config_monitor", None) with direct attribute access in config_path setter
- Remove unintentional double @Property decorator on project_folder

* fix: widen worker and evaluate-network error handling

- Catch BaseException in Worker.run() so SystemExit from CLI functions
  is marshalled to the UI instead of silently killing the thread
- Wrap the full evaluate_network method in a single try/except Exception
  so runtime errors (GPU OOM, corrupted models, etc.) are consistently
  reported through show_task_error instead of only catching config errors

* refactor: replace QTimer.singleShot with explicit named reload timers
- Add named _reload_timer members to AnalyzeVideos and ManageProject tabs
  so the timer is inspectable in tests and auto-cancels on tab destruction
- Wire editor.accepted to timer.start instead of a fire-and-forget lambda

* Add `MainWindow.invalidate_config_cache()`

a lightweight hook to force the next cfg access to re-read and validate from disk. Can be called from outside the GUI as well (e.g. after video analysis or training network, in case they manipulate te config)

* test: add coverage for show_task_error, cache invalidation, and reload timer

- Add test_task_error.py: verify generic vs config-error dialog rendering
  and that the 'Open configuration' button only appears for config errors
- Test invalidate_config_cache drops the cached config for the next access
  and is safe to call with no project loaded
- Test that the named _reload_timer (replacing QTimer.singleShot) reliably
  fires the reload callback

* widen train_network error handling, similar to 4472fd3

* deliberately narrow down config errors. (exclude TypeError and ValueError)

* watch config file parent directory to detect atomic replacements

Connect to the directoryChanged signal and add the parent directory
to the watched paths in set_path().  Some editors atomically replace
files (delete + rename), which silently drops a file-only watch in
QFileSystemWatcher.  Watching the parent catches those changes and
re-adds the file path in _check_for_change() as before.

* guard pose_cfg.get("method") string-type

* Add a self._extract_error flag.

The error signal sets it to True. _show_success_message checks it and skips the dialog entirely if there was an error.

* update tests with narrow error types

* Revert narrowing of CONFIG_ERRORS - treat only ValidationError as config-related in show_task_error

CONFIG_LOAD_ERRORS includes FileNotFoundError, PermissionError,
OSError, TypeError, and ValueError — all of which can originate
from non-config sources (e.g. missing checkpoint, disk full,
wrong type from a GUI callback) when raised by worker threads.
Showing a config-themed dialog with an "Open configuration"
button for those errors was misleading.

Now show_task_error only trusts ValidationError (which is always
from config parsing) to decide on the config dialog.  The
config-loading recovery loop continues to use the full
CONFIG_LOAD_ERRORS tuple where the context is known.

Restore TypeError and ValueError to CONFIG_LOAD_ERRORS so the
recovery loop properly catches those as user-repairable config
errors.

* fix MainWindow init _config_monitor

…-handler