The docs editor currently drops inline-style toolbar actions when no
text is selected. Introduce a small view-local controller that holds
a pending style anchored to a caret position. Subsequent edits in
the editor / text-editor will consume this state to apply the style
to typed characters and clear it on non-typing caret moves.

Wire the PendingStyle controller into the docs editor input pipeline.
applyStyle and clearInlineFormatting now record a pending style on a
collapsed caret, getSelectionStyle merges it so toolbar buttons reflect
the toggle, and the text editor consumes the style on each insertText
via small docInsertText / docDeleteText / docSplitBlock helpers that
wrap doc mutations with the pending hooks. IME composing and Hangul
cycles preserve the anchor via rewindAnchor; Enter splits via
rebindAnchor. Non-typing caret moves (mouse, arrow keys, Home/End,
clipboard ops, blur, undo, redo, inline image insert) clear the
pending state. Integration scenarios cover collapsed toggle, caret
move discard, Enter preservation, IME composing, layered toggles,
and anchor-mismatch clearing.

Record implementation notes and deviations from the written plan
(setPendingStyle setter instead of constructor option; centralized
helpers instead of per-call-site wiring; bundled Task 2+3 commit
because the unused field tripped the pre-commit typecheck) so the
next contributor in this area has the why, not just the what.

Wire pending.clear() at four caret-moving sites the first pass missed:
validateCursorPosition (cursor reset after remote block delete),
resetAfterDocumentReplace (snapshot restore from peer), image-body
mousedown (capture-phase handler runs before text-editor sees the
click), Tab cell navigation, and handleKeyDown's remote-block-deleted
fallback. Anchor-mismatch covered these functionally, but the design
doc lists each one as an explicit cancellation trigger and skipping
them left a brief window where the toolbar would show a stale toggle
after a remote edit or image click. Add an editor-level wiring spec
(`pending-style-editor.test.ts`) that exercises the public EditorAPI
so future refactors that drop a clear() call fail a test.

The toolbar path (editor.applyStyle) was wired for pending, but the
keyboard shortcut path goes through text-editor.toggleStyle /
clearFormatting which both early-returned on a collapsed selection.
That meant Cmd+B with no selection did nothing — and re-pressing
Cmd+B never toggled off because the first press was a no-op. Route
both methods through pending.set when collapsed, reading the visual
style (caret style + any existing pending) so re-toggles operate on
the displayed state rather than the stale doc-level style.

Add keyboard-path coverage to pending-style-editor.test.ts:
collapsed Cmd+B sets bold, Cmd+B twice toggles off, Cmd+B + Cmd+I
accumulates, and Cmd+\ clears.

Second-pass review surfaced that the design doc never mentioned the
keyboard-shortcut entry point (text-editor.toggleStyle /
clearFormatting), which is exactly why the original implementation
shipped without it wired and required a follow-up after browser
smoke. Capture the missed-surface lesson in the lessons file and
update the design doc's Architecture section to list both surfaces
explicitly. Add a defense-in-depth comment to toggleStyle explaining
that the unguarded visual merge depends on selection-creating paths
having cleared pending, and wire pending.clear() at the one such
path (selectAll) that was still missing it.