SidebarSystem migration: Search panel (results tree)

[JDonaghy]

Summary

Migrate the Search panel's results tree section from hand-rolled scroll/selection/collapse to quadraui::compose::SidebarSystem.

The Search panel is a hybrid: a Form (query/replace inputs + toggle buttons) sits above a TreeView of file-grouped results. It already uses build_search_panel_msv() which builds a 2-section MSV (Form + Results). The SidebarSystem migration targets the results tree section only — the Form interaction (text input cursors, toggle buttons, Replace All) stays as engine-managed state.

Prereqs

• SidebarSystem: compose helper for MSV + TreeView sidebar panels quadraui#63 — SidebarSystem shipped

Engine fields replaced by SidebarSystem

Field	Purpose	SidebarSystem equivalent
project_search_selected	flat row index in results	per-section selection
search_file_expanded: Vec<bool>	per-file collapse state	SidebarSystem internal collapse
search_has_focus (partial)	keyboard focus for results tree	SidebarSystem focus state
search_panel_msv_layout	cached MSV layout	SidebarSystem layout

Fields that remain (domain-specific): project_search_query, project_search_results, project_search_options, project_search_running, project_search_receiver, project_replace_text, project_replace_running, project_replace_receiver, search_panel_form_focus, search_query_caret, replace_text_caret.

Migration steps

1. Define a SidebarSectionDef for "results" (single-section SidebarSystem, or 1 section per result file)
2. Each frame: call sidebar.set_rows("results", rows) from the results tree portion of build_search_panel_msv()
3. Replace results-tree navigation in handle_search_key() with sidebar.handle() + SidebarEvent::RowSelected
4. Keep Form-mode interaction (query input, replace input, toggles) separate — intercept before SidebarSystem when form has focus
5. Remove the 4 engine fields listed above
6. TUI + GTK: replace bespoke results-tree paint with sidebar.render(backend, rect)
7. Update tests in search.rs

Design note

The Search panel's Form + Tree hybrid means SidebarSystem manages only the lower half. The form and results tree share a single MSV today — after migration, the form renders independently (via quadraui::Form) and the results tree uses SidebarSystem. This is cleaner than the current monolithic MSV approach.

Key files

• src/core/engine/mod.rs — remove 4 engine fields
• src/core/engine/search.rs — replace tree navigation in handle_search_tree_hit(), handle_search_key()
• src/render.rs — split build_search_panel_msv() into form + SidebarSystem tree
• src/tui_main/panels.rs — replace search panel render
• src/main.rs — replace GTK search panel render

Reference

See JDonaghy/quadraui#63 for the complete migration guide with code examples.

[JDonaghy]

Blocked on quadraui#105

Filed JDonaghy/quadraui#105 to add SectionBody::Form support to SidebarSystem. This lets the search panel use a single 2-section SidebarSystem (Form + Tree) instead of a hybrid approach, maximizing dedup.

Once quadraui#105 lands, this migration becomes:

• 2-section SidebarSystem: SectionKind::Form (chrome) + SectionKind::Tree (results)
• Single sidebar.render() + sidebar.handle() per backend — no form-vs-tree branching
• Unified dispatch_search_sidebar_key_unified() in engine
• ~155 net lines removed (including TUI: remove duplicate search panel focus state (use engine's search_panel_form_focus) #333 and Unify search panel results-mode behavior: typing should re-enter input mode on both backends #334 folded in)