Add a tree-based category panel that supports expand/collapse of categories.
Introduces CatTreeEntry and build_cat_tree to render categories as
a collapsible tree. The category panel now displays categories with
expand indicators (▶/▼) and shows items under expanded categories.
CmdContext gains cat_tree_entry(), cat_at_cursor(), and cat_tree_len()
methods to work with the tree. App tracks expanded_cats in a HashSet.
Keymap updates: Enter in category panel now triggers filter-to-item.
Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/Qwen3.5-35B-A3B-GGUF:Q5_K_M)
Define Effect trait in ui/effect.rs with concrete effect structs for
all model mutations, view changes, navigation, and app state updates.
Each effect implements apply(&self, &mut App). Add App::apply_effects
to apply a sequence of effects. No behavior change yet — existing
key handlers still work as before.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Removes dead use statements across dispatch, formula, import, model, and
UI modules. Prefixes intentionally unused variables with _ in app.rs,
analyzer.rs, and grid.rs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
