[Miodec]

Stacked on #8563 (T3): base is refactor/caret-boundary, retarget to master once that merges.

Summary

Roadmap T4: the word registry becomes private to Words. Only the overflow check stays exported.

 src/ts/
 ├── states/
-│   └── word-elements.ts        # module-level word + line break maps, LETTER_SELECTOR
 └── components/pages/test/
+    ├── word-registry.ts        # createWordRegistry(), one per Words
+    ├── selectors.ts            # LETTER_SELECTOR
     ├── Words.tsx               # creates the registry
     ├── Word.tsx                # registers through a `register` prop
     ├── words-layout.ts         # gets the registry as an option
     └── caret.ts                # no registry access

 <Words>
+  registry = createWordRegistry()
-  createWordsLayout({ words, wordsWrapper, caret, paceCaret })
+  createWordsLayout({ registry, words, wordsWrapper, caret, paceCaret })
-  <Word word isActive />                      // registerWordElement() global
+  <Word word isActive register={registry.registerWord} />
-  <LineBreak index />                         // registerLineBreakElements() global
+  <LineBreak index register={registry.registerLineBreak} />

 caret.goTo({
   wordIndex,
+  wordEl: registry.getWord(wordIndex),       // the layout passes the element
 })

wouldActiveWordOverflow (used by before-insert-text) reads the registry of the mounted Words, and returns true when none is mounted.

Evidence

• Tests: all 107 files pass, including the test-page harness (27 tests). New word-registry.spec.ts covers the guard that keeps a remount's element when the old one's cleanup runs after it. words-wrapper-height.spec builds its own registry. The two Words.spec tests that read the global registry are gone; the existing rendered-output tests cover the same cases.
• Browser (__mt.checkLayout()): [] after load, line jumps, tape mode (letter) with the pace caret on, and 25 extra letters. Caret offset 2–4px.
• Overflow guard: at font size 6, typing 30 extra letters stopped at 21, with the word's top and height unchanged.

Merge Danger

Door: two-way

Internal refactor; reverting restores the global module.

Blast Radius: test-words

No visible change. The caret position, the line jump, the tape scroll and the extra-letter overflow block all read through the new registry, so a miss there shows up as a stuck caret or a wrapping word.

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