feat(tui-go): make the ? overlay list every keybind

Audited handleNormalKey / handleApprovalKey / the OverlayDiff handler against the
help cheat-sheet and found gaps: enter, ↑↓/jk, /, s, c, a, w, q and ? itself were
bound but undocumented. Reorganise helpBody into navigate / session / overlays /
approval band / diff-viewer groups covering all of them. help_complete_test.go
asserts a row exists for every binding so the help can't silently drift from the
handlers. The longer sheet scrolls fine via the modal-scroll support.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/tui-go/internal/app/help_complete_test.go

@@ -0,0 +1,60 @@
+package app
+
+import (
+	"strings"
+	"testing"
+)
+
+// Every key the TUI binds (normal mode, approval band, and the diff/preview viewer) must
+// have a row in the ? overlay. Keyed by a distinctive description phrase so deleting a row
+// fails loudly here — keep this list in step with handleNormalKey / handleApprovalKey and
+// the OverlayDiff handler whenever a binding is added or changed.
+func TestHelpCoversEveryKeybind(t *testing.T) {
+	m := inSessionModel(120, 80)
+	help := strings.Join(m.helpBody(), "\n")
+
+	want := []string{
+		// navigate
+		"move the session / list selection",    // ↑↓ / j k
+		"open the selected session",            // enter
+		"filter the session list",              // /
+		"jump to your previous / next message", // ^↑ / ^↓
+		"scroll output",                        // PgUp / PgDn (+ ^u / ^d)
+		"drop selection",                       // esc
+		"back to the session list",             // l
+		// session
+		"compose a message",                 // i
+		"toggle chat / steering mode",       // s
+		"show workflows",                    // w
+		"copy the selected message",         // y
+		"open the latest diff / preview",    // ^x
+		"cancel the running session",        // c
+		"re-open a dismissed approval gate", // a
+		"quit",                              // q
+		// overlays
+		"command palette",          // p
+		"this keybindings help",    // ?
+		"event inspector",          // e
+		"tools / artifacts",        // t / v
+		"resume past sessions",     // S / R
+		"swap model / edit config", // m / g
+		"grants / idea board",      // G / I
+		// approval band
+		"approve once",                          // y / a / enter
+		"reject",                                // n / r
+		"steer (add a note)",                    // e / s
+		"approve-always",                        // A
+		"walk the pending queue",                // ↑ / ↓
+		"fullscreen the diff / command preview", // ^x
+		"dismiss for now",                       // esc
+		// diff / preview viewer
+		"scroll a line",     // ↑ / ↓
+		"scroll a page",     // PgUp / PgDn
+		"jump to top / end", // g / G
+	}
+	for _, w := range want {
+		if !strings.Contains(help, w) {
+			t.Errorf("? help is missing a row for %q", w)
+		}
+	}
+}

apps/tui-go/internal/app/overlays.go

@@ -818,20 +818,31 @@ func (m Model) helpBody() []string {
 		}
 		out = append(out, "")
 	}
-	section("session", []kb{
+	section("navigate", []kb{
-		{"i", "compose a message"},
+		{"↑↓ / j k", "move the session / list selection"},
+		{"enter", "open the selected session"},
+		{"/", "filter the session list"},
 		{"^↑ / ^↓", "jump to your previous / next message"},
-		{"y", "copy the selected message (OSC52)"},
 		{"PgUp / PgDn", "scroll output (^u / ^d half-page)"},
 		{"esc", "drop selection / scroll → follow newest"},
-		{"^x", "open the latest diff"},
 		{"l", "back to the session list"},
 	})
+	section("session", []kb{
+		{"i", "compose a message"},
+		{"s", "toggle chat / steering mode"},
+		{"w", "show workflows (idle screen)"},
+		{"y", "copy the selected message (OSC52)"},
+		{"^x", "open the latest diff / preview"},
+		{"c", "cancel the running session"},
+		{"a", "re-open a dismissed approval gate"},
+		{"q", "quit"},
+	})
 	section("overlays", []kb{
-		{"p", "command palette (shows all shortcuts)"},
+		{"p", "command palette (all shortcuts)"},
+		{"?", "this keybindings help"},
 		{"e", "event inspector (/ to filter)"},
 		{"t / v", "tools / artifacts"},
-		{"S / R", "session stats / resume sessions"},
+		{"S / R", "session stats / resume past sessions"},
 		{"m / g", "swap model / edit config"},
 		{"G / I", "grants / idea board"},
 	})
@@ -842,6 +853,7 @@ func (m Model) helpBody() []string {
 		{"A", "approve-always — choose scope"},
 		{"↑ / ↓", "walk the pending queue"},
 		{"^x", "fullscreen the diff / command preview"},
+		{"esc", "dismiss for now (a re-opens)"},
 	})
 	section("diff / preview viewer (^x)", []kb{
 		{"↑ / ↓", "scroll a line"},