feat(tui): retire the permanent /help pin from the metrics line

An always-on key hint held the right edge of the metrics row forever
(founder, 2026-09-08). The posture bar above already owns contextual hints
and retiring status toasts, so the pin is removed and the row spends its
width on facts.

Tests: cargo test -p codewhale-tui --lib tui::ui:: -> 816 passed, 0 failed;
tui::infoline:: -> 11 passed, 0 failed.

crates/tui/src/tui/ui/frame.rs

@@ -355,8 +355,10 @@ fn render_info_row(f: &mut Frame, app: &mut App, area: Rect) -> InfoLineInteract
             })
             .map(|hb| hb.id)
     });
-    let help_hint = crate::tui::shell_key_routing::info_help_hint(app.ui_locale);
-    let info = InfoLine::new(&app.ui_theme, &help_hint, &segments)
+    // The permanent `/help` pin left the metrics line (founder, 2026-09-08):
+    // an always-on key hint is noise. Contextual hints and retiring status
+    // toasts live in the posture bar above, which already owns them.
+    let info = InfoLine::new(&app.ui_theme, "", &segments)
         .ascii_safe(crate::tui::color_compat::ascii_safe_enabled())
         .hovered(hovered)
         .compact(app.metrics_line == crate::config::ChromeRowPreset::Compact);

crates/tui/src/tui/ui/frame/one_owner_tests.rs

@@ -157,10 +157,8 @@ fn composed_frame_paints_each_fact_in_exactly_one_row() {
             ("model", model),
             ("cost", super::session_cost_label(&app)),
             ("agent count", "2 agents".to_string()),
-            (
-                "help hint",
-                crate::tui::shell_key_routing::info_help_hint(app.ui_locale),
-            ),
+            // The permanent `/help` pin is gone (founder, 2026-09-08): the
+            // metrics line no longer paints a key hint at all.
             ("output rate", "40 avg tok/s".to_string()),
             ("ttft", "ttft 400ms".to_string()),
         ];