Unify result context menus between grid and list layouts

[multiplex55]

Motivation

• Ensure grid-mode result tiles expose the same context-menu actions and side effects as list-mode items to avoid parity bugs and duplicated logic.
• Reduce duplication by extracting the branch-heavy list-mode menu construction into a shared helper so future menu changes only need one place to be updated.
• Preserve existing activation/geometry behavior (left-click activation, grid cols/col_width/ui.end_row) while keeping refresh/focus side effects intact.

Description

• Added a ResultContextMenuKind enum to classify actionable result kinds (folder, bookmark, timer, stopwatch, snippet, tempfile, note, clipboard, todo, default).
• Implemented result_context_menu_kind(&self, action: &Action) -> ResultContextMenuKind to deterministically map Action entries to menu kinds.
• Implemented attach_result_context_menu(&mut self, action: &Action, menu_resp: egui::Response, refresh: &mut bool, set_focus: &mut bool) -> egui::Response that builds the full context menu UI and preserves all branch-specific behaviors (folders, bookmarks, notes/todos, snippets, timers/stopwatches, clipboard entries, Edit App, pin/unpin) and mutates refresh/set_focus when appropriate.
• Updated grid rendering so each tile Response is passed through attach_result_context_menu before click handling; list rendering also now uses the same helper (menu geometry and left-click activation unchanged).
• Added focused tests in the module to capture parity/regression intent: grid_context_menu_eligibility_uses_result_actions, context_menu_parity_bookmark_between_list_and_grid, and context_menu_parity_todo_between_list_and_grid.

Testing

• Ran cargo fmt to format the code and succeeded.
• Added unit tests that exercise the pure helper (result_context_menu_kind) and assert parity between list and grid classifications.
• Attempted to run targeted tests (cargo test grid_context_menu -- --nocapture), but the build failed due to a missing system dependency for a transitive crate: the system alsa pkg-config file (alsa.pc) is not available in this environment, causing the test run to error before tests could execute.

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Codex Task