fix(renderer): stabilize preserveLineBreaks whitespace and newline rendering

docs/subagents/INDEX.md

@@ -25,3 +25,4 @@ Read first. Keep concise.
 | `codex-preserve-linebreak-display-20260220T110436Z-r8f1` | `codex-preserve-linebreak-display` | `Fix visible overlay display artifact when subtitleStyle.preserveLineBreaks is disabled` | `completed` | `docs/subagents/agents/codex-preserve-linebreak-display-20260220T110436Z-r8f1.md` | `2026-02-20T11:10:51Z` |
 | `codex-review-refactor-cleanup-20260220T113818Z-i2ov` | `codex-review-refactor-cleanup` | `Review recent TASK-85 refactor effort and identify remaining cleanup work` | `handoff` | `docs/subagents/agents/codex-review-refactor-cleanup-20260220T113818Z-i2ov.md` | `2026-02-20T11:48:28Z` |
 | `codex-commit-unstaged-20260220T115057Z-k7q2` | `codex-commit-unstaged` | `Commit all current unstaged repository changes with content-derived conventional message` | `in_progress` | `docs/subagents/agents/codex-commit-unstaged-20260220T115057Z-k7q2.md` | `2026-02-20T11:51:18Z` |
+| `codex-overlay-whitespace-newline-20260221T040705Z-aw2j` | `codex-overlay-whitespace-newline` | `Fix visible overlay whitespace/newline token rendering bug with TDD regression coverage` | `completed` | `docs/subagents/agents/codex-overlay-whitespace-newline-20260221T040705Z-aw2j.md` | `2026-02-21T04:18:16Z` |

docs/subagents/agents/codex-overlay-whitespace-newline-20260221T040705Z-aw2j.md

@@ -0,0 +1,38 @@
+# Agent Log: codex-overlay-whitespace-newline-20260221T040705Z-aw2j
+
+- alias: codex-overlay-whitespace-newline
+- mission: Fix visible overlay whitespace/newline token rendering bug (blank hoverable tokens) with regression tests.
+- status: completed
+- started_utc: 2026-02-21T04:07:05Z
+- last_update_utc: 2026-02-21T04:14:30Z
+
+## Intent
+- Reproduce bug around spaces/newlines + `preserveLineBreaks` in visible overlay.
+- Add failing renderer/tokenization regression tests first.
+- Patch render/token mapping to avoid hoverable blank tokens and preserve-mode duplication.
+
+## Touched Files
+- src/renderer/subtitle-render.ts
+- src/renderer/subtitle-render.test.ts
+- docs/subagents/INDEX.md
+- docs/subagents/collaboration.md
+- docs/subagents/agents/codex-overlay-whitespace-newline-20260221T040705Z-aw2j.md
+
+## Decisions
+- Ignore whitespace-only token surfaces in source alignment.
+- Non-preserve mode: flatten token newlines to spaces, whitespace-only surfaces as text nodes.
+- Preserve mode alignment: skip unmatched token surfaces (do not append fallback token) to avoid duplicate tail text.
+
+## Verification
+- RED: new whitespace-separator test failed before fix.
+- GREEN: renderer suite pass after first fix.
+- RED: new preserve-mode duplicate-tail mismatch test failed before fix.
+- GREEN: `bun run build && node dist/renderer/subtitle-render.test.js` pass (11/11).
+- GREEN: `node --test dist/renderer/subtitle-render.test.js` pass.
+
+## Blockers
+- none
+
+## Next Step
+- User visual verify with `preserveLineBreaks=true` + known mixed-width numeral lines.
+- [2026-02-21T04:18:16Z] follow-up: fixed non-token first-paint behavior to collapse line breaks when `preserveLineBreaks=false` (`normalizeSubtitle(..., collapseLineBreaks=true)` in fallback path); added regression test for normalize collapse.

docs/subagents/collaboration.md

@@ -16,3 +16,7 @@ Shared notes. Append-only.
 - [2026-02-20T11:04:36Z] [codex-preserve-linebreak-display-20260220T110436Z-r8f1|codex-preserve-linebreak-display] overlap note: touching `src/renderer/subtitle-render.ts` + renderer tests to fix preserve-linebreaks disabled display artifact while preserving TASK-91 behavior.
 - [2026-02-20T11:07:29Z] [codex-preserve-linebreak-display-20260220T110436Z-r8f1|codex-preserve-linebreak-display] completed follow-up for TASK-91: non-preserve mode now flattens token CR/LF to spaces instead of emitting `<br>` from token surfaces; regression test added.
 - [2026-02-20T11:10:51Z] [codex-preserve-linebreak-display-20260220T110436Z-r8f1|codex-preserve-linebreak-display] second follow-up: handle overlap token streams by aligning non-preserve rendering to normalized source text and skipping unmatched tail tokens (prevents duplicated second-line phrase).
+- [2026-02-21T04:07:05Z] [codex-overlay-whitespace-newline-20260221T040705Z-aw2j|codex-overlay-whitespace-newline] overlap note: touching `src/renderer/subtitle-render.ts` + renderer tests for whitespace/newline display/token hover regression around `preserveLineBreaks`.
+- [2026-02-21T04:09:02Z] [codex-overlay-whitespace-newline-20260221T040705Z-aw2j|codex-overlay-whitespace-newline] completed: whitespace-only token surfaces no longer become token segments; non-preserve mode now flattens token newlines to spaces and renders whitespace as text nodes; added regression test in renderer suite.
+- [2026-02-21T04:14:30Z] [codex-overlay-whitespace-newline-20260221T040705Z-aw2j|codex-overlay-whitespace-newline] preserve-line-breaks follow-up: when token surface mismatches source (e.g., `1` vs `１`), alignment now skips unmatched token instead of appending both source tail + token; fixes duplicated no-break line artifact.
+- [2026-02-21T04:18:16Z] [codex-overlay-whitespace-newline-20260221T040705Z-aw2j|codex-overlay-whitespace-newline] follow-up fix: non-token fallback now honors preserveLineBreaks flag by collapsing line breaks when disabled; prevents visible multi-line -> single-line transition while tokenized payload arrives.