feat(tui-go): global input history + stop idle redraws (copy-safe)

Input history is now a single global ring (recordInput) shared by every input surface —
free-chat, the workflow-intent line, and in-session chat — so ↑/↓ recalls anything you've
sent, including outside a session (previously per-session, so idle/intent had none).

Copy fix: the 120ms animation tick now only runs while something actually animates
(animating(): active session spinner, blinking caret, reconnect). Init no longer starts it
unconditionally; tickKick (re)starts it on demand and tickMsg stops it when idle. An idle
screen no longer auto-redraws, so a native terminal text selection survives instead of being
wiped every frame. Tests cover the ring (dedup/cap/cross-context walk) and the idle gate.

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

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

@@ -228,9 +228,9 @@ type Model struct {
 	inputMode    InputMode
 	inputBuffer  string
 	inputCursor  int
-	history      map[string][]string
-	historyIndex int
-	savedBuffer  string
+	inputHistory []string // submitted lines across all contexts (chat, intent, in-session), newest last
+	historyIndex int      // -1 = editing the live buffer; else an index into inputHistory
+	savedBuffer  string   // live buffer stashed while walking history
 
 	// flow flags
 	sessionEntered       bool
@@ -302,7 +302,10 @@ type Model struct {
 	paletteIndex  int
 
 	// animation
-	frame int // tick counter; drives spinner + caret blink
+	frame   int  // tick counter; drives spinner + caret blink
+	ticking bool // true while a tick loop is scheduled. The loop is gated on animating()
+	// so an idle screen stops redrawing — which lets native terminal selection survive
+	// (the 120ms redraw used to wipe a mouse drag every frame).
 
 	// snapshot phase
 	snapshotPhase bool
@@ -338,7 +341,6 @@ func NewModel(client *ws.Client) Model {
 		theme:           NewTheme(SoftBlue),
 		wfIndex:         -1,
 		inputMode:       ModeRouter,
-		history:         map[string][]string{},
 		historyIndex:    -1,
 		routerMessages:  map[string][]RouterEntry{},
 		configStaged:    map[string]string{},