feat(tui-go): transcript message-jump + OSC52 copy

ctrl+↑/↓ jumps between your sent (user) messages in the transcript: ctrl+↑ from the
bottom selects the most recent, steps to older ones (clamping); ctrl+↓ steps back and
drops to tail-follow past the last. The selected message is highlighted and scrolled
into view (routerRows tracks per-message row offsets and windows to the selection).

`y` yanks the selected message — or the latest turn when none is selected — to the
system clipboard over OSC52 (go-osc52, tmux-wrapped under $TMUX), which is SSH/Termius-
safe unlike a mouse drag. A brief "✓ copied" footer note animates out (and self-stops
the tick). esc drops the selection; switching sessions clears it. Tests cover the
user-message jump/clamp/tail and the copy-text selection.

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

apps/tui-go/go.mod

@@ -3,6 +3,7 @@ module github.com/correx/tui-go
 go 1.24.2
 
 require (
+	github.com/aymanbagabas/go-osc52/v2 v2.0.1
 	github.com/charmbracelet/bubbletea v1.3.10
 	github.com/charmbracelet/glamour v1.0.0
 	github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834
@@ -13,7 +14,6 @@ require (
 
 require (
 	github.com/alecthomas/chroma/v2 v2.20.0 // indirect
-	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/aymerick/douceur v0.2.0 // indirect
 	github.com/charmbracelet/colorprofile v0.4.1 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.15 // indirect