Write: Replace highlight-to-format with persistent top toolbar (#48305)

* feat: replace highlight-to-format toolbar with persistent top toolbar

Replace the floating selection-based formatting toolbar with a persistent
toolbar fixed below the topbar, always visible on the Write page.

- Toolbar always visible (no show/hide logic, no animation)
- Heading dropdown (Normal, H2, H3) with state-based label
- Inline formatting: bold, italic, underline, strikethrough
- Text color picker with 6 preset colors (default resets without
  stripping other formatting)
- Text alignment: left, center, right (with div cleanup)
- Lists: ordered and unordered
- Link, blockquote, and image buttons
- Highlight text + paste URL creates a link automatically
- Horizontally scrollable on mobile with JS-positioned dropdowns
- Fade-in on dropdown menus only
- Updated convertToBlocks to handle lists, text-align, and color markup
- Added 6 new PHP tests for toolbar markup and state
- Higher z-index and broader chrome-hiding for Atomic compatibility
- Use filemtime for asset versioning to bust CDN cache on changes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: toolbar dropdown polish — animation jump, click-outside, cache busting

- Fix color menu and link popover horizontal jump caused by fade-in
  animation overriding the translateX(-50%) centering transform
- Add click-outside-to-close for heading and color dropdowns
- Use max(view.js, style.css) mtime for cache version so CSS-only
  changes also bust the cache
- Remove orphaned JSDoc block

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: use non-centered fade-in animation for mobile dropdowns

On mobile, color menu and link popover use transform: none instead of
translateX(-50%), so override the animation back to bw-fade-in to
prevent the centered animation from fighting the mobile positioning.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: toolbar polish — color mismatch, listener leaks, link input, quote alignment

- Align default text color to #1a1a1a across JS/PHP/CSS (was #333333 in JS)
- Fix event listener leak in heading and color dropdown close handlers
- Update heading label immediately when selecting from dropdown
- Bind link input value to state so it clears properly between uses
- Use getAttribute('href') instead of .href for raw link values
- Close link popover on click-outside
- Serialize text alignment on blockquote blocks
- Bump heading dropdown caret from 10px to 12px

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: prevent link popover close handler leak on toggle-off

Use a module-level variable for the link popover click-outside handler,
matching the pattern already used by heading and color menu dropdowns.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: link popover — allow text selection in input, fix reopen after apply

Two fixes for the link popover:

1. preventToolbarBlur now skips inputs/textareas so users can select
   and interact with the URL text using the mouse.

2. applyLink, removeLink, and handleLinkKeyDown now clean up the
   click-outside handler and refocus the content area, so the link
   popover can be reopened immediately after applying a link.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

projects/packages/jetpack-mu-wpcom/changelog/add-persistent-top-toolbar

@@ -0,0 +1,4 @@
+Significance: minor
+Type: changed
+
+Write: Replace highlight-to-format floating toolbar with a persistent top toolbar.