nx_caption_burn.nx

nx_caption_burn.nx -- burn a caption (e.g. a translated subtitle) onto a video FRAME (Framebuffer): an opaque caption BAR across the bottom + the caption text centered, integer scale, NO float. Composes the proven bits-up paint substrate (nx_paint_solid_rect + nx_paint_text_scaled over the 5x7 bitmap font). A caption TRACK = timestamped [t0,t1) segments; cb_active_at(t) selects the on-screen line (or -1). This is the live-translation RENDER core -- ASR (speech->text) + open-domain MT are RESEARCHER long-poles; the phrase-table MT (nx_mt_phrasetable) feeds it translated bytes for the gated R1 vertical. license_tier: ORIGINAL