Persist note details visibility preference

[multiplex55]

Motivation

• Remember whether note metadata/details are shown so new and existing users get consistent behavior across sessions.
• Expose the preference in the settings editor so users can change the default without editing files.
• Ensure note panels open with the configured default and persist user toggles to settings so the last runtime choice is retained.

Description

• Added a persisted note_show_details: bool to Settings with #[serde(default = "default_note_show_details")] and wired default_note_show_details() into impl Default for Settings so the missing field defaults to false (details hidden). (file: src/settings.rs)
• Extended SettingsEditor with a note_show_details field, hydrated it in from_settings(...), included it in to_settings(...), and added a checkbox labeled "Show note details by default" under the existing "Note settings" section. (file: src/settings_editor.rs)
• Propagated runtime state by adding note_show_details to LauncherApp, threading it through update_paths(...), initializing it from loaded settings, and using it when creating note panels via NotePanel::from_note_with_details(note, self.note_show_details). (file: src/gui/mod.rs)
• Implemented a from_note_with_details(...) constructor and a set_show_metadata(...) helper on NotePanel and added write-through persistence on toggles so clicking Hide/Show Details updates Settings.note_show_details on disk only when the state actually changes and surfaces load/save errors via app.set_error(...). (file: src/gui/note_panel.rs)
• Added unit tests: serialization/default tests for note_show_details and note-panel tests for constructor behavior, toggle persistence (writes only on change), and existing metadata visibility gating. (files: src/settings.rs, src/gui/note_panel.rs)
• Touched plugin/application glue to include the new setting in plugin-editor flows so the value is persisted/applied when changing settings. (file: src/plugin_editor.rs)

Testing

• Verified code formatting with cargo fmt -- --check, which succeeded.
• Added and attempted to run unit tests for note_show_details and note panel behavior, but cargo test in this environment failed due to an external system dependency (the alsa system library / pkg-config is missing which triggers alsa-sys build failures), so the new tests could not be executed end-to-end here.
• The repository changes include the new tests and they should pass in a normal developer environment with system build dependencies installed (or in CI that provides them).

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Codex Task