feat(tui): composer soft-wrap, alt+backspace, bracketed paste, borderless input

- editorLines now soft-wraps long logical lines at the box width (caret tracked
  across wrapped rows) instead of overflowing/truncating
- alt+backspace deletes the word before the cursor (deleteWordBack)
- handle tea.PasteMsg so bracketed paste (Ctrl+V / Ctrl+Shift+V / right-click)
  drops clipboard text into the focused composer; was silently dropped
- render the composer (in-session + launcher) borderless: top rule + flush text,
  no side borders or trailing padding, so a terminal drag-copy yields just the
  typed text instead of box chrome and whitespace

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

@@ -3,6 +3,7 @@ package app
 import (
 	"fmt"
 	"os"
+	"sort"
 	"strings"
 	"time"
 
@@ -120,6 +121,11 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.applyTasksLoaded(msg)
 		return m, nil
 
+	case tea.PasteMsg:
+		// Bracketed paste (Ctrl+V / Ctrl+Shift+V / right-click): drop the clipboard text into
+		// whichever composer is focused. Without this the paste is silently swallowed.
+		return m.handlePaste(msg.Content), m.tickKick()
+
 	case tea.KeyPressMsg:
 		next, cmd := m.handleKey(toKeyMsg(msg))
 		// A keypress may have entered a typing/active state (insert mode, steering, …);
@@ -142,6 +148,9 @@ func (m *Model) applySessionsLoaded(msg sessionsLoadedMsg) {
 	}
 	m.sessionListErr = ""
 	m.sessionList = msg.sessions
+	sort.Slice(m.sessionList, func(i, j int) bool {
+		return m.sessionList[i].LastActivityAt > m.sessionList[j].LastActivityAt
+	})
 	if m.sessionListIndex >= len(m.sessionList) {
 		m.sessionListIndex = 0
 	}
@@ -473,7 +482,11 @@ func (m Model) handleInsertKey(k keyMsg) (tea.Model, tea.Cmd) {
 		}
 		return m, nil
 	case keyBackspace:
-		m.backspace()
+		if k.Alt {
+			m.deleteWordBack()
+		} else {
+			m.backspace()
+		}
 		m.syncFilter()
 	case keyLeft:
 		if m.inputCursor > 0 {
@@ -1210,6 +1223,20 @@ func (m Model) execPalette(id string) (tea.Model, tea.Cmd) {
 
 // --- input editing ---
 
+// handlePaste inserts pasted clipboard text into the focused composer (steering note or the
+// main input). Newlines are preserved — the input buffer is multi-line and editorLines wraps it.
+func (m Model) handlePaste(s string) tea.Model {
+	switch {
+	case s == "":
+	case m.steering:
+		m.steerBuffer += s
+	case m.editMode == ModeInsert && m.overlay == OverlayNone:
+		m.appendRunes(s)
+		m.syncFilter()
+	}
+	return m
+}
+
 func (m *Model) appendRunes(s string) {
 	b := m.inputBuffer
 	c := m.inputCursor
@@ -1229,6 +1256,24 @@ func (m *Model) backspace() {
 	m.inputCursor = c - 1
 }
 
+// deleteWordBack removes the word before the cursor (Alt+Backspace): first any run of
+// spaces, then the run of non-space chars, all left of the cursor.
+func (m *Model) deleteWordBack() {
+	c := m.inputCursor
+	if c > len(m.inputBuffer) {
+		c = len(m.inputBuffer)
+	}
+	i := c
+	for i > 0 && m.inputBuffer[i-1] == ' ' {
+		i--
+	}
+	for i > 0 && m.inputBuffer[i-1] != ' ' {
+		i--
+	}
+	m.inputBuffer = m.inputBuffer[:i] + m.inputBuffer[c:]
+	m.inputCursor = i
+}
+
 // cycleLauncherWf advances the idle launch target: 0 = chat, 1..N = workflows[i-1], wrapping.
 func (m *Model) cycleLauncherWf() {
 	m.launcherWf = (m.launcherWf + 1) % (len(m.workflows) + 1)