feat(subtitles): add line-break display toggle and narrow-space normalization

docs/subagents/agents/codex-narrow-space-tokenizer-20260220T061716Z-p97s.md

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+# Agent: `codex-narrow-space-tokenizer-20260220T061716Z-p97s`
+
+- alias: `codex-narrow-space-tokenizer`
+- mission: `Fix narrow/invisible subtitle spacing causing incorrect tokenizer boundaries.`
+- status: `done`
+- branch: `main`
+- started_at: `2026-02-20T06:17:31Z`
+- heartbeat_minutes: `5`
+
+## Current Work (newest first)
+- [2026-02-20T06:20:07Z] handoff: normalized invisible separators in tokenizer input; added regression test; targeted tests green.
+- [2026-02-20T06:19:20Z] test: `bun run build && node --test dist/subtitle/stages/normalize.test.js` (pass, 1/1); `node --test dist/core/services/tokenizer.test.js` (pass, 43/43).
+- [2026-02-20T06:18:38Z] edit: updated `normalizeTokenizerInput` to map `U+200B/U+2060/U+FEFF` to regular spaces before whitespace collapsing.
+- [2026-02-20T06:18:02Z] test: added failing regression for subtitle sample with `\u200B` separator.
+- [2026-02-20T06:17:31Z] intent: create TASK-90; TDD-first regression for narrow Unicode spacing in subtitle line `キリキリと かかってこい`.
+- [2026-02-20T06:17:31Z] progress: coordination started; index row added; scanning tokenizer normalization points next.
+
+## Files Touched
+- `docs/subagents/INDEX.md`
+- `docs/subagents/agents/codex-narrow-space-tokenizer-20260220T061716Z-p97s.md`
+- `docs/subagents/collaboration.md`
+- `backlog/tasks/task-90 - Normalize-narrow-Unicode-whitespace-in-tokenizer-input.md`
+- `src/subtitle/stages/normalize.ts`
+- `src/subtitle/stages/normalize.test.ts`
+
+## Assumptions
+- issue likely Unicode spacing code point treated as token boundary.
+- target behavior: collapse/normalize narrow spacing to standard spacing before lookup token grouping.
+
+## Open Questions / Blockers
+- possible overlap with TASK-85 refactor touching tokenizer paths.
+
+## Next Step
+- done.

docs/subagents/agents/codex-preserve-linebreaks-20260220T063538Z-s4nd.md

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+# Agent: `codex-preserve-linebreaks-20260220T063538Z-s4nd`
+
+- alias: `codex-preserve-linebreaks`
+- mission: `Add config option to preserve subtitle line breaks in visible overlay rendering.`
+- status: `done`
+- branch: `main`
+- started_at: `2026-02-20T06:35:38Z`
+- heartbeat_minutes: `5`
+
+## Current Work (newest first)
+- [2026-02-20T06:42:51Z] handoff: TASK-91 complete; added config flag `subtitleStyle.preserveLineBreaks` (default false), renderer token-linebreak alignment path, tests/docs/examples updated.
+- [2026-02-20T06:42:20Z] test: `bun run build && node --test dist/config/config.test.js dist/renderer/subtitle-render.test.js` pass (43/43); macOS helper compile falls back due sandboxed Swift cache write.
+- [2026-02-20T06:41:07Z] edit: added `alignTokensToSourceText` helper + preserve-line-break render path in `src/renderer/subtitle-render.ts`; state/config plumbing added.
+- [2026-02-20T06:39:34Z] test: added config parse/warn coverage + renderer helper newline-segment test.
+- [2026-02-20T06:35:38Z] intent: create backlog ticket; implement opt-in config flag default-off; keep current normalization default behavior.
+- [2026-02-20T06:35:38Z] progress: located normalization/render paths in `src/core/services/tokenizer.ts` and `src/renderer/subtitle-render.ts`.
+
+## Files Touched
+- `docs/subagents/INDEX.md`
+- `docs/subagents/agents/codex-preserve-linebreaks-20260220T063538Z-s4nd.md`
+- `docs/subagents/collaboration.md`
+- `backlog/tasks/task-91 - Add-config-toggle-to-preserve-visible-overlay-subtitle-line-breaks.md`
+- `src/types.ts`
+- `src/config/definitions.ts`
+- `src/config/service.ts`
+- `src/config/config.test.ts`
+- `src/renderer/state.ts`
+- `src/renderer/subtitle-render.ts`
+- `src/renderer/subtitle-render.test.ts`
+- `docs/configuration.md`
+- `config.example.jsonc`
+- `docs/public/config.example.jsonc`
+
+## Assumptions
+- request targets visible overlay rendering parity with MPV line breaks.
+- default behavior must remain whitespace-collapsed for tokenizer/texthooker consistency.
+
+## Open Questions / Blockers
+- none.
+
+## Next Step
+- done.