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/state/who.rs

@@ -5,6 +5,8 @@
 
 use lore::core::who_types::WhoResult;
 
+use crate::text_width::{next_char_boundary, prev_char_boundary};
+
 // ---------------------------------------------------------------------------
 // WhoMode
 // ---------------------------------------------------------------------------
@@ -291,24 +293,6 @@ impl WhoState {
     }
 }
 
-/// Find the byte offset of the previous char boundary.
-fn prev_char_boundary(s: &str, pos: usize) -> usize {
-    let mut i = pos.saturating_sub(1);
-    while i > 0 && !s.is_char_boundary(i) {
-        i -= 1;
-    }
-    i
-}
-
-/// Find the byte offset of the next char boundary.
-fn next_char_boundary(s: &str, pos: usize) -> usize {
-    let mut i = pos + 1;
-    while i < s.len() && !s.is_char_boundary(i) {
-        i += 1;
-    }
-    i
-}
-
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------