Add RELEASE_NOTES/v0.8.3.md (real-time collaboration, presentation
decks, runtime asset slimming, device-level theme, the Chrome web
capture inbox) and mirror the feature/roadmap updates — plus the Chrome
Web Store link — across README.md and all 14 translations.
GitHub releases were named by bare tag because the action got no name.
The note's leading heading is the natural title, so publish it as the
release name and drop it from the body instead of repeating it.
The notes stopped at the 2026-07-23 state and never described the design
agent at all, despite it carrying the largest share of the v0.8.2 work.
Add the multi-screen generation, geometry-repair, provider/skill, and
large-document canvas performance sections, plus the image-crop, stroke
ordering, right-rail, and Windows save changes landed since.
