feat(tui): add per-screen responsive layout helpers

Introduce breakpoint-aware helper functions in layout.rs that
centralize per-screen responsive decisions. Each function maps a
Breakpoint to a screen-specific value, replacing scattered
hardcoded checks across view modules:

- detail_side_panel: show discussions side panel at Lg+
- info_screen_columns: 1 column on Xs/Sm, 2 on Md+
- search_show_project: hide project path column on narrow terminals
- timeline_time_width: compact time on Xs (5), full on Md+ (12)
- who_abbreviated_tabs: shorten tab labels on Xs/Sm
- sync_progress_bar_width: scale progress bar 15→50 with width

All functions are const fn with exhaustive match arms.
Includes 6 unit tests covering every breakpoint variant.

crates/lore-tui/src/layout.rs

@@ -44,6 +44,84 @@ pub const fn show_preview_pane(bp: Breakpoint) -> bool {
     }
 }
 
+// ---------------------------------------------------------------------------
+// Per-screen responsive helpers
+// ---------------------------------------------------------------------------
+
+/// Whether detail views (issue/MR) should show a side panel for discussions.
+///
+/// At `Lg`+ widths, enough room exists for a 60/40 or 50/50 split with
+/// description on the left and discussions/cross-refs on the right.
+#[inline]
+pub const fn detail_side_panel(bp: Breakpoint) -> bool {
+    match bp {
+        Breakpoint::Lg | Breakpoint::Xl => true,
+        Breakpoint::Xs | Breakpoint::Sm | Breakpoint::Md => false,
+    }
+}
+
+/// Number of stat columns for the Stats/Doctor screens.
+///
+/// - `Xs` / `Sm`: 1 column (full-width stacked)
+/// - `Md`+: 2 columns (side-by-side sections)
+#[inline]
+pub const fn info_screen_columns(bp: Breakpoint) -> u16 {
+    match bp {
+        Breakpoint::Xs | Breakpoint::Sm => 1,
+        Breakpoint::Md | Breakpoint::Lg | Breakpoint::Xl => 2,
+    }
+}
+
+/// Whether to show the project path column in search results.
+///
+/// On narrow terminals, the project path is dropped to give the title
+/// more room.
+#[inline]
+pub const fn search_show_project(bp: Breakpoint) -> bool {
+    match bp {
+        Breakpoint::Xs | Breakpoint::Sm => false,
+        Breakpoint::Md | Breakpoint::Lg | Breakpoint::Xl => true,
+    }
+}
+
+/// Width allocated for the relative-time column in timeline events.
+///
+/// Narrow terminals get a compact time (e.g., "2h"), wider terminals
+/// get the full relative time (e.g., "2 hours ago").
+#[inline]
+pub const fn timeline_time_width(bp: Breakpoint) -> u16 {
+    match bp {
+        Breakpoint::Xs => 5,
+        Breakpoint::Sm => 8,
+        Breakpoint::Md | Breakpoint::Lg | Breakpoint::Xl => 12,
+    }
+}
+
+/// Whether to use abbreviated mode-tab labels in the Who screen.
+///
+/// On narrow terminals, tabs are shortened to 3-char abbreviations
+/// (e.g., "Exp" instead of "Expert") to fit all 5 modes.
+#[inline]
+pub const fn who_abbreviated_tabs(bp: Breakpoint) -> bool {
+    match bp {
+        Breakpoint::Xs | Breakpoint::Sm => true,
+        Breakpoint::Md | Breakpoint::Lg | Breakpoint::Xl => false,
+    }
+}
+
+/// Width of the progress bar in the Sync screen.
+///
+/// Scales with terminal width to use available space effectively.
+#[inline]
+pub const fn sync_progress_bar_width(bp: Breakpoint) -> u16 {
+    match bp {
+        Breakpoint::Xs => 15,
+        Breakpoint::Sm => 25,
+        Breakpoint::Md => 35,
+        Breakpoint::Lg | Breakpoint::Xl => 50,
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------
@@ -99,4 +177,60 @@ mod tests {
     fn test_lore_breakpoints_matches_defaults() {
         assert_eq!(LORE_BREAKPOINTS, Breakpoints::DEFAULT);
     }
+
+    // -- Per-screen responsive helpers ----------------------------------------
+
+    #[test]
+    fn test_detail_side_panel() {
+        assert!(!detail_side_panel(Breakpoint::Xs));
+        assert!(!detail_side_panel(Breakpoint::Sm));
+        assert!(!detail_side_panel(Breakpoint::Md));
+        assert!(detail_side_panel(Breakpoint::Lg));
+        assert!(detail_side_panel(Breakpoint::Xl));
+    }
+
+    #[test]
+    fn test_info_screen_columns() {
+        assert_eq!(info_screen_columns(Breakpoint::Xs), 1);
+        assert_eq!(info_screen_columns(Breakpoint::Sm), 1);
+        assert_eq!(info_screen_columns(Breakpoint::Md), 2);
+        assert_eq!(info_screen_columns(Breakpoint::Lg), 2);
+        assert_eq!(info_screen_columns(Breakpoint::Xl), 2);
+    }
+
+    #[test]
+    fn test_search_show_project() {
+        assert!(!search_show_project(Breakpoint::Xs));
+        assert!(!search_show_project(Breakpoint::Sm));
+        assert!(search_show_project(Breakpoint::Md));
+        assert!(search_show_project(Breakpoint::Lg));
+        assert!(search_show_project(Breakpoint::Xl));
+    }
+
+    #[test]
+    fn test_timeline_time_width() {
+        assert_eq!(timeline_time_width(Breakpoint::Xs), 5);
+        assert_eq!(timeline_time_width(Breakpoint::Sm), 8);
+        assert_eq!(timeline_time_width(Breakpoint::Md), 12);
+        assert_eq!(timeline_time_width(Breakpoint::Lg), 12);
+        assert_eq!(timeline_time_width(Breakpoint::Xl), 12);
+    }
+
+    #[test]
+    fn test_who_abbreviated_tabs() {
+        assert!(who_abbreviated_tabs(Breakpoint::Xs));
+        assert!(who_abbreviated_tabs(Breakpoint::Sm));
+        assert!(!who_abbreviated_tabs(Breakpoint::Md));
+        assert!(!who_abbreviated_tabs(Breakpoint::Lg));
+        assert!(!who_abbreviated_tabs(Breakpoint::Xl));
+    }
+
+    #[test]
+    fn test_sync_progress_bar_width() {
+        assert_eq!(sync_progress_bar_width(Breakpoint::Xs), 15);
+        assert_eq!(sync_progress_bar_width(Breakpoint::Sm), 25);
+        assert_eq!(sync_progress_bar_width(Breakpoint::Md), 35);
+        assert_eq!(sync_progress_bar_width(Breakpoint::Lg), 50);
+        assert_eq!(sync_progress_bar_width(Breakpoint::Xl), 50);
+    }
 }