refactor(tui): group view state into sub-structs, add spawn_job helper

[Samanyu-dev]

Summary

Addresses #107. Two changes to src/ui/tui.rs:

1. Group view state into owned sub-structs

App had 40+ flat fields, and five view types each carried their own copy of the same selected/scroll/select_next/select_prev pattern (proc_list_*, tree_*, histogram_*, settings_*, pointer_tree_*). Selection/scroll state is now a shared ViewState, and each view owns one:

#[derive(Default)]
struct ViewState {
    pub selected: usize,
    pub scroll: usize,
}

impl ViewState {
    fn next(&mut self, max: usize, wrap: bool) { ... }
    fn prev(&mut self, max: usize, wrap: bool) { ... }
}

struct AllocTreeView {
    pub rows: Vec<TreeDisplayRow>,
    pub collapsed: std::collections::HashSet<u32>,
    pub total_memory: u64,
    pub state: ViewState,
}

App now holds proc_list: ProcListView, alloc_tree: AllocTreeView, pointer_tree: PointerTreeView, histogram: HistogramView, hex_dump: HexDumpView, settings_view: SettingsView instead of ~19 loose fields, and the five duplicated *_select_next/*_select_prev impls collapse into calls like:

Focus::Tree => self.alloc_tree.state.next(self.alloc_tree.rows.len(), false),
HeapViewMode::Histogram => self.histogram.state.next(SIZE_BUCKETS.len(), false),

2. spawn_job helper for command dispatch

handle_command had eight near-identical "spawn thread → run command → send AppEvent" blocks (baseline, diff <proc>, diff <a> <b>, save, leak, leak-m, and both scan variants), each repeating the same thread-spawn boilerplate. Added:

fn spawn_job<F>(tx: std::sync::mpsc::Sender<AppEvent>, job: F)
where
    F: FnOnce(std::sync::mpsc::Sender<AppEvent>) -> Result<(), String> + Send + 'static,
{
    std::thread::spawn(move || {
        if let Err(e) = job(tx.clone()) {
            tx.send(AppEvent::Output(Line::raw(format!("error: {}", e)))).ok();
        }
    });
}

Each command's closure keeps whatever success/error events it needs to send (e.g. scan still sends ScanError on failure so is_loading resets correctly), it just no longer has to write the std::thread::spawn(move || { ... }) wrapper by hand:

["baseline", _proc] => {
    let proc = _proc.to_string();
    spawn_job(self.tx.clone(), move |tx| {
        let result = commands::scan(vec!["scan", &proc, "-h"])?;
        tx.send(AppEvent::BaseLine(result)).ok();
        tx.send(AppEvent::Output(Line::raw("Baseline set".to_string()))).ok();
        Ok(())
    });
}

No behavioral changes — this is a pure state/structure refactor to make the file easier to extend and read.

Test plan

• cargo build — clean, no new warnings
• cargo test — 108/108 lib tests + 10/10 integration tests pass
• cargo fmt -- --check src/ui/tui.rs — clean
• cargo clippy --lib — no new warnings introduced

🤖 Generated with Claude Code

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[SickleFire]

LGTM! Good refactor on src/ui/tui.rs

Approved!