Upgrade MyGo to v0.5.5

MyGo v0.5.5 returns ui.Element as a checked value handle instead of a
pointer. Migrated with `mygo migrate-ui`, then fixed what the codemod
leaves to review:

- Element nil checks become .Valid(); absent elements are ui.Element{}.
- Input handlers and paint callbacks run outside the build pass, where
  elements expire and Context methods are inert: read IsDisabled into a
  local during the build, keep a ui.Handle for Focus, use c.Services()
  for clipboard access, create ui.Local state during the build.
- Add core.AutoFocus: v0.5.5 records an overlay's opener after its
  content builds, so same-frame autofocus lost focus restore on close.
  It focuses one frame later; cascader rows defer their focus likewise.
- core.OverlayLayer identifies build passes by the root element, not
  c.Now(), which repeats across passes and under the Tester clock.
- Context menus survive the opening press counted as PressedOutside;
  split button tooltip no longer reorders its open menu; disabled
  menubar rows pass presses to the panel; Form defers blur-started
  async checks so the growing message no longer moves Submit away
  from the release; Combobox drops its disabled copy now that MyGo
  blocks typing under a disabled wrapper (canary flipped to a guard).
- The Tester clock is virtual: tests use Advance/Now instead of
  time.Sleep/time.Now and read element state inside the view. The web
  mirror advances the clock to wall time before each frame and input.
- AGENTS.md and docs describe the value Element API and the new pin.

Snapshot goldens are darwin-only and were not re-verified here.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

git/ansi_text.go

@@ -17,7 +17,7 @@ type AnsiTextOptions struct {
 }
 
 // AnsiText renders terminal output with its SGR styles.
-func AnsiText(c *ui.Context, text string, opts AnsiTextOptions) *ui.Element {
+func AnsiText(c *ui.Context, text string, opts AnsiTextOptions) ui.Element {
 	k := core.Tokens(c)
 	col := ui.Column(c).Font(theme.MonoFont).TextColor(k.Text).Shrink(0)
 	col.Children(func() {

git/blame_view.go

@@ -40,7 +40,7 @@ type BlameViewOptions struct {
 }
 
 // BlameView shows code with its commits; give it a height.
-func BlameView(c *ui.Context, s *BlameViewState, lines []BlameLine, opts BlameViewOptions) *ui.Element {
+func BlameView(c *ui.Context, s *BlameViewState, lines []BlameLine, opts BlameViewOptions) ui.Element {
 	var first *BlameLine
 	if len(lines) > 0 {
 		first = &lines[0]

git/blame_view_test.go

@@ -58,7 +58,7 @@ func TestBlameViewHoverDetails(t *testing.T) {
 	}, 700, 340)
 	r, _ := tt.Find("Uika")
 	tt.Move(r.X+2, r.Y+2)
-	time.Sleep(650 * time.Millisecond)
+	tt.Advance(650 * time.Millisecond)
 	tt.Move(r.X+3, r.Y+2)
 	tt.Frame()
 	if tt.HasText(gitTestHash(2) + "\nUika · 2026-10-05\nComment the lanes") {

git/branch_selector.go

@@ -23,7 +23,7 @@ type BranchSelectorOptions struct {
 
 // BranchSelectorResult is a built BranchSelector and its events.
 type BranchSelectorResult struct {
-	Element *ui.Element
+	Element ui.Element
 	changed bool
 	create  string
 }
@@ -82,7 +82,7 @@ func BranchSelector(c *ui.Context, selected *string, branches []Branch, opts Bra
 		ui.Icon(c, icons.Must("chevrons-up-down")).Size(14, 14).TextColor(k.TextMuted)
 	})
 	b := tr.Bounds()
-	ui.PopoverBase(c, tr, &s.open, func(panel *ui.Element) {
+	ui.PopoverBase(c, tr, &s.open, func(panel ui.Element) {
 		core.OverlayStyle(c, panel, overlay.OverlayAnchored(c, panel, b))
 		panel.Margin(6, 0, 0, 0).Padding(u * 2).Gap(u * 2).Width(300).MaxHeight(overlay.PopoverRoom(c, b)).AlignItems(ui.Stretch)
 		var first *Branch
@@ -100,7 +100,7 @@ func BranchSelector(c *ui.Context, selected *string, branches []Branch, opts Bra
 		}
 		in := input.TextInput(c, &s.query, input.TextInputOptions{Placeholder: core.Msg(c, "branch_selector.search"), Label: core.Msg(c, "branch_selector.search"),
 			Leading: func() { ui.Icon(c, icons.Must("search")).Size(14, 14).TextColor(k.TextMuted) }})
-		in.Input.AutoFocus()
+		core.AutoFocus(c, in.Input)
 		if in.Changed() {
 			s.hl, s.reveal = 0, true
 		}

git/changes_list.go

@@ -78,7 +78,7 @@ func ChangesList(c *ui.Context, s *ChangesListState, files []ChangedFile, opts C
 	}
 	prev := s.cursor
 	outer := ui.Column(c).AlignItems(ui.Stretch).Disabled(opts.Disabled)
-	var e *ui.Element
+	var e ui.Element
 	outer.Children(func() {
 		restore := data.DataSelectTheme(c, 0)
 		defer restore()

git/command_block.go

@@ -24,7 +24,7 @@ type CommandBlockOptions struct {
 
 // CommandBlockResult is a built CommandBlock and its events.
 type CommandBlockResult struct {
-	Element *ui.Element
+	Element ui.Element
 	toggled bool
 	copied  string
 }

git/commit_input.go

@@ -31,7 +31,7 @@ type CommitInputOptions struct {
 
 // CommitInputResult is a built CommitInput and its events.
 type CommitInputResult struct {
-	Element          *ui.Element
+	Element          ui.Element
 	committed, amend bool
 }
 

git/commit_list.go

@@ -24,7 +24,7 @@ type Commit struct {
 
 // GitListResult is a built version-control list and its events.
 type GitListResult struct {
-	Element            *ui.Element
+	Element            ui.Element
 	changed, submitted bool
 	action, item       string
 }

git/diff_stat.go

@@ -17,7 +17,7 @@ type DiffStatOptions struct {
 }
 
 // DiffStat shows added and deleted counts with a ratio bar.
-func DiffStat(c *ui.Context, added, deleted int, opts DiffStatOptions) *ui.Element {
+func DiffStat(c *ui.Context, added, deleted int, opts DiffStatOptions) ui.Element {
 	if added < 0 || deleted < 0 {
 		panic("mujica: DiffStat counts must not be negative")
 	}

git/diff_viewer.go

@@ -42,7 +42,7 @@ type diffViewerRow struct {
 }
 
 // DiffViewer compares two texts by line; give it a height.
-func DiffViewer(c *ui.Context, s *DiffViewerState, from, to string, opts DiffViewerOptions) *ui.Element {
+func DiffViewer(c *ui.Context, s *DiffViewerState, from, to string, opts DiffViewerOptions) ui.Element {
 	ctx := opts.Context
 	if ctx == 0 {
 		ctx = 3

git/git_status_badge.go

@@ -38,7 +38,7 @@ type GitStatusBadgeOptions struct {
 }
 
 // GitStatusBadge marks a status by letter, outline and color.
-func GitStatusBadge(c *ui.Context, status GitStatus, opts GitStatusBadgeOptions) *ui.Element {
+func GitStatusBadge(c *ui.Context, status GitStatus, opts GitStatusBadgeOptions) ui.Element {
 	k := core.Tokens(c)
 	name := core.Msg(c, "git_status_badge."+gitStatusKeys[gitStatusIndex(status)])
 	col := gitStatusColor(k, status)

git/inline_diff.go

@@ -21,7 +21,7 @@ type inlineDiffCache struct {
 }
 
 // InlineDiff shows old and new lines with changed words marked.
-func InlineDiff(c *ui.Context, from, to string, opts InlineDiffOptions) *ui.Element {
+func InlineDiff(c *ui.Context, from, to string, opts InlineDiffOptions) ui.Element {
 	k := core.Tokens(c)
 	col := ui.Column(c).AlignItems(ui.Stretch).Shrink(0).Radius(theme.ControlRadius).Clip()
 	cache := ui.Local(col, "words", func() *inlineDiffCache { return &inlineDiffCache{} })

git/review_comment.go

@@ -39,7 +39,7 @@ type ReviewCommentOptions struct {
 
 // ReviewCommentResult is a built ReviewComment and its events.
 type ReviewCommentResult struct {
-	Element            *ui.Element
+	Element            ui.Element
 	reply              string
 	resolved, reopened bool
 }

git/three_way_merge.go

@@ -187,7 +187,7 @@ func threeWayMergeChunk(c *ui.Context, s *ThreeWayMergeState, i int) bool {
 }
 
 // mergeChoiceButton is a toggle marking the chosen side.
-func mergeChoiceButton(c *ui.Context, label string, on bool) *ui.Element {
+func mergeChoiceButton(c *ui.Context, label string, on bool) ui.Element {
 	k := core.Tokens(c)
 	u := core.Density(c).Unit()
 	b := ui.ButtonBase(c).MinHeight(theme.MinHitSize).Padding(0, u*3).Gap(u*1.5).Radius(theme.ControlRadius).