Add British voiceover to all six knowledge-work demos

[AlexMikhalev]

The six published editor and knowledge-work demos had captions but no spoken guidance. Add locally generated British female Emma narration, synchronized with the demonstrated actions, to Chrome, Firefox, Safari, stock Zed, paired grep search/synthesis, and overview videos.

All six compressed video streams remain identical to the reviewed paced-v2 originals. Speech runs at its natural rate with fixed per-take gain and scheduled silence. Public narration.json records scripts, timing, take hashes and qualification; the manifest binds its digest and final media bytes. Pages disclose the synthetic voice and link the script.

Validation: 12 website tests pass; pinned Zola0.22.1 build passes; all six final MP4s decode; independently transcribed encoded audio scores0.9853–1.0 across videos. Individual take transcription mean0.9942, minimum0.9091; all takes fit their scenes. Independent source/media review confirms script/manifest hashes, actual judgment query wording, unchanged video bitstreams and disclosed output limits.

This publishes narrated previews. It does not claim complete41-requirement acceptance, Safari drag repair, stock Zed visual parity, shared CLI visibility of document-scoped synonyms, or corrected synthesis overstatement. Recorded source identity remains unchanged; the Zed fork stays separate.