feat(tui): Phase 4 completion + Phase 5 session/lock/text-width

Phase 4 (bd-1df9) — all 5 acceptance criteria met:
- Sync screen with delta ledger (bd-2x2h, bd-y095)
- Doctor screen with health checks (bd-2iqk)
- Stats screen with document counts (bd-2iqk)
- CLI integration: lore tui subcommand (bd-26lp)
- CLI integration: lore sync --tui flag (bd-3l56)

Phase 5 (bd-3h00) — session persistence + instance lock + text width:
- text_width.rs: Unicode-aware measurement, truncation, padding (16 tests)
- instance_lock.rs: Advisory PID lock with stale recovery (6 tests)
- session.rs: Atomic write + CRC32 checksum + quarantine (9 tests)

Closes: bd-26lp, bd-3h00, bd-3l56, bd-1df9, bd-y095

crates/lore-tui/src/view/scope_picker.rs

@@ -0,0 +1,276 @@
+//! Scope picker overlay — modal project filter selector.
+//!
+//! Renders a centered modal listing all available projects. The user
+//! selects "All Projects" or a specific project to filter all screens.
+
+use ftui::core::geometry::Rect;
+use ftui::render::cell::{Cell, PackedRgba};
+use ftui::render::drawing::{BorderChars, Draw};
+use ftui::render::frame::Frame;
+
+use crate::state::scope_picker::ScopePickerState;
+use crate::state::ScopeContext;
+
+use super::{ACCENT, BG_SURFACE, BORDER, TEXT, TEXT_MUTED};
+
+/// Selection highlight background.
+const SELECTION_BG: PackedRgba = PackedRgba::rgb(0x3A, 0x3A, 0x34);
+
+// ---------------------------------------------------------------------------
+// render_scope_picker
+// ---------------------------------------------------------------------------
+
+/// Render the scope picker overlay centered on the screen.
+///
+/// Only renders if `state.visible`. The modal is 50% width, up to 40x20.
+pub fn render_scope_picker(
+    frame: &mut Frame<'_>,
+    state: &ScopePickerState,
+    current_scope: &ScopeContext,
+    area: Rect,
+) {
+    if !state.visible {
+        return;
+    }
+    if area.height < 5 || area.width < 20 {
+        return;
+    }
+
+    // Modal dimensions.
+    let modal_width = (area.width / 2).clamp(25, 40);
+    let row_count = state.row_count();
+    // +3 for border top, title gap, border bottom.
+    let modal_height = ((row_count + 3) as u16).clamp(5, 20).min(area.height - 2);
+
+    let modal_x = area.x + (area.width.saturating_sub(modal_width)) / 2;
+    let modal_y = area.y + (area.height.saturating_sub(modal_height)) / 2;
+    let modal_rect = Rect::new(modal_x, modal_y, modal_width, modal_height);
+
+    // Clear background.
+    let bg_cell = Cell {
+        fg: TEXT,
+        bg: BG_SURFACE,
+        ..Cell::default()
+    };
+    for y in modal_rect.y..modal_rect.bottom() {
+        for x in modal_rect.x..modal_rect.right() {
+            frame.buffer.set(x, y, bg_cell);
+        }
+    }
+
+    // Border.
+    let border_cell = Cell {
+        fg: BORDER,
+        bg: BG_SURFACE,
+        ..Cell::default()
+    };
+    frame.draw_border(modal_rect, BorderChars::ROUNDED, border_cell);
+
+    // Title.
+    let title = " Project Scope ";
+    let title_x = modal_x + (modal_width.saturating_sub(title.len() as u16)) / 2;
+    let title_cell = Cell {
+        fg: ACCENT,
+        bg: BG_SURFACE,
+        ..Cell::default()
+    };
+    frame.print_text_clipped(title_x, modal_y, title, title_cell, modal_rect.right());
+
+    // Content area (inside border).
+    let content_x = modal_x + 1;
+    let content_max_x = modal_rect.right().saturating_sub(1);
+    let content_width = content_max_x.saturating_sub(content_x);
+    let first_row_y = modal_y + 1;
+    let max_rows = (modal_height.saturating_sub(2)) as usize; // Inside borders.
+
+    // Render rows.
+    let visible_end = (state.scroll_offset + max_rows).min(row_count);
+    for vis_idx in 0..max_rows {
+        let row_idx = state.scroll_offset + vis_idx;
+        if row_idx >= row_count {
+            break;
+        }
+
+        let y = first_row_y + vis_idx as u16;
+        let selected = row_idx == state.selected_index;
+
+        let bg = if selected { SELECTION_BG } else { BG_SURFACE };
+
+        // Fill row background.
+        if selected {
+            let sel_cell = Cell {
+                fg: TEXT,
+                bg,
+                ..Cell::default()
+            };
+            for x in content_x..content_max_x {
+                frame.buffer.set(x, y, sel_cell);
+            }
+        }
+
+        // Row content.
+        let (label, is_active) = if row_idx == 0 {
+            let active = current_scope.project_id.is_none();
+            ("All Projects".to_string(), active)
+        } else {
+            let project = &state.projects[row_idx - 1];
+            let active = current_scope.project_id == Some(project.id);
+            (project.path.clone(), active)
+        };
+
+        // Active indicator.
+        let prefix = if is_active { "> " } else { "  " };
+
+        let fg = if is_active { ACCENT } else { TEXT };
+        let cell = Cell {
+            fg,
+            bg,
+            ..Cell::default()
+        };
+
+        // Truncate label to fit.
+        let max_label_len = content_width.saturating_sub(2) as usize; // 2 for prefix
+        let display = if label.len() > max_label_len {
+            format!("{prefix}{}...", &label[..label.floor_char_boundary(max_label_len.saturating_sub(3))])
+        } else {
+            format!("{prefix}{label}")
+        };
+
+        frame.print_text_clipped(content_x, y, &display, cell, content_max_x);
+    }
+
+    // Scroll indicators.
+    if state.scroll_offset > 0 {
+        let arrow_cell = Cell {
+            fg: TEXT_MUTED,
+            bg: BG_SURFACE,
+            ..Cell::default()
+        };
+        frame.print_text_clipped(
+            content_max_x.saturating_sub(1),
+            first_row_y,
+            "^",
+            arrow_cell,
+            modal_rect.right(),
+        );
+    }
+    if visible_end < row_count {
+        let arrow_cell = Cell {
+            fg: TEXT_MUTED,
+            bg: BG_SURFACE,
+            ..Cell::default()
+        };
+        let bottom_y = first_row_y + (max_rows as u16).saturating_sub(1);
+        frame.print_text_clipped(
+            content_max_x.saturating_sub(1),
+            bottom_y,
+            "v",
+            arrow_cell,
+            modal_rect.right(),
+        );
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::scope::ProjectInfo;
+    use ftui::render::grapheme_pool::GraphemePool;
+
+    macro_rules! with_frame {
+        ($width:expr, $height:expr, |$frame:ident| $body:block) => {{
+            let mut pool = GraphemePool::new();
+            let mut $frame = Frame::new($width, $height, &mut pool);
+            $body
+        }};
+    }
+
+    fn sample_projects() -> Vec<ProjectInfo> {
+        vec![
+            ProjectInfo {
+                id: 1,
+                path: "alpha/repo".into(),
+            },
+            ProjectInfo {
+                id: 2,
+                path: "beta/repo".into(),
+            },
+        ]
+    }
+
+    #[test]
+    fn test_render_hidden_noop() {
+        with_frame!(80, 24, |frame| {
+            let state = ScopePickerState::default();
+            let scope = ScopeContext::default();
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+            // Should not panic.
+        });
+    }
+
+    #[test]
+    fn test_render_visible_no_panic() {
+        with_frame!(80, 24, |frame| {
+            let mut state = ScopePickerState::default();
+            let scope = ScopeContext::default();
+            state.open(sample_projects(), &scope);
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+        });
+    }
+
+    #[test]
+    fn test_render_with_selection() {
+        with_frame!(80, 24, |frame| {
+            let mut state = ScopePickerState::default();
+            let scope = ScopeContext::default();
+            state.open(sample_projects(), &scope);
+            state.select_next(); // Move to first project
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+        });
+    }
+
+    #[test]
+    fn test_render_tiny_terminal_noop() {
+        with_frame!(15, 4, |frame| {
+            let mut state = ScopePickerState::default();
+            let scope = ScopeContext::default();
+            state.open(sample_projects(), &scope);
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+            // Should not panic on tiny terminals.
+        });
+    }
+
+    #[test]
+    fn test_render_active_scope_highlighted() {
+        with_frame!(80, 24, |frame| {
+            let mut state = ScopePickerState::default();
+            let scope = ScopeContext {
+                project_id: Some(2),
+                project_name: Some("beta/repo".into()),
+            };
+            state.open(sample_projects(), &scope);
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+        });
+    }
+
+    #[test]
+    fn test_render_empty_project_list() {
+        with_frame!(80, 24, |frame| {
+            let mut state = ScopePickerState::default();
+            let scope = ScopeContext::default();
+            state.open(vec![], &scope);
+            let area = frame.bounds();
+            render_scope_picker(&mut frame, &state, &scope, area);
+            // Only "All Projects" row, should not panic.
+        });
+    }
+}