Polish chrome and rework tab-switch repaint

Module renamed github.com/harrybrwn/patterm → github.com/hjbdev/patterm
across imports.

Chrome:
- Palette redrawn with rounded box-drawing borders, accent left-bar
  for the selected item, dim hints, and a separator-aware footer.
- Tab bar grew from 1 row to 3: labels with breathing room, a dim
  argv subtitle truncated to each tab's width, and an accent thick
  underline for the focused tab with a faint divider extending across
  the rest of the host width. Layout, viewport-renderer, and screen-
  renderer tests updated for the new mainTop.
- Sidebar reuses the same palette: accent section headers, `▎`
  selection marker, `●`/`○` status glyphs, dim previews.
- Shared SGR constants moved into internal/app/style.go.

Palette input:
- Adjacent duplicate arrow events (legacy `\x1b[B` + kitty
  `\x1b[57353u` for one keypress, or two of the same form) are now
  collapsed via peekArrowEvent + chunk-level dedupe in processStdin.
- On open, push `\x1b[>0u` onto the host's kitty keyboard stack so
  palette input is in plain legacy mode regardless of what the child
  pushed (codex/ratatui pushes its own flags which had been leaking
  to the host). Popped on close.

Tab-switch repaint (repaintFocused):
- Use the emulator's SerializeVT bytes (with SGR / cursor / DECSTBM
  / tabstops) instead of plain text, fed through the per-focused
  viewport renderer so the shifter translates row positions.
- Prelude resets host SGR / DECOM / DECSTBM (pinned to viewport) /
  cursor visibility before the replay, so leftover modes from the
  previously-focused child don't distort the new snapshot.
- Re-emit the saved cursor as a child-space CUP after the
  serialized bytes so the host cursor lands at the emulator's
  actual position (overriding DECSTBM's home side-effect and the
  tabstop-setup CHA sequences) AND the renderer's vr.row/vr.col
  get re-synced via trackCSI.
- cursorShifter now carries childRows and rewrites empty
  `\x1b[r` to `\x1b[<mainTop>;<mainBottom>r` (host coords) — the
  default (1,1) shifted to (4,4) was producing a one-row scrolling
  region that scroll-exploded the replay.
- After the snapshot lands, nudge the focused child with a one-row
  PTY winsize toggle so the kernel emits SIGWINCH and ratatui-style
  TUIs throw away their diff state and emit a fresh frame.

Codex still renders incorrectly after a focus switch; see TODO.md
"Switch-back render divergence" for the deep investigation handoff.

internal/app/palette_input_test.go

@@ -3,7 +3,7 @@ package app
 import (
 	"testing"
 
-	"github.com/harrybrwn/patterm/internal/preset"
+	"github.com/hjbdev/patterm/internal/preset"
 )
 
 func newTestPalette() *paletteState {
@@ -106,3 +106,34 @@ func TestPaletteLegacyPrintableTypes(t *testing.T) {
 		t.Fatalf("query %q", string(p.query))
 	}
 }
+
+// peekArrowEvent powers the chunk-level dedupe in processStdin. The
+// scenarios below cover the patterns we've actually seen terminals
+// emit for one physical Down press: a kitty press event, a legacy CSI
+// arrow, and the pair of the two adjacent. We assert classification
+// here so processStdin can rely on it.
+func TestPeekArrowEventClassifies(t *testing.T) {
+	cases := []struct {
+		name    string
+		in      []byte
+		wantNav byte
+		wantLen int
+	}{
+		{"legacy down", []byte("\x1b[B"), 'D', 3},
+		{"legacy up", []byte("\x1b[A"), 'U', 3},
+		{"kitty down press", []byte("\x1b[57353u"), 'D', 8},
+		{"kitty up press", []byte("\x1b[57352u"), 'U', 8},
+		{"kitty down release", []byte("\x1b[57353;1:3u"), 0, 12},
+		{"kitty enter", []byte("\x1b[13u"), 0, 0},
+		{"not a CSI", []byte("a"), 0, 0},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			nav, adv := peekArrowEvent(tc.in, 0)
+			if nav != tc.wantNav || adv != tc.wantLen {
+				t.Fatalf("got nav=%q len=%d, want nav=%q len=%d",
+					nav, adv, tc.wantNav, tc.wantLen)
+			}
+		})
+	}
+}