feat(media): plugin tour videos with burned-in captions (#188)

[srsholmes]

Closes #188 (video capture tooling) and adds captioned demo tours for the whole plugin lineup.

Tooling — scripts/capture-videos.ts

Drives the running overlay over CDP (Page.startScreencast → ffmpeg → animated WebP):

• Per-plugin tours (default): each plugin ships plugins/<id>/tour.json — a scripted tour with captions burned in as a lower-third (ffmpeg drawtext, timed to real frame durations). Opt-in: no tour.json → no tour. Per-tour fps/width so art-heavy library grids stay small.
• Review → promote: capture:videos --tours records to a gitignored review folder; --promote=<id> copies the clip into plugins/<id>/assets/demo.webp and inserts a ## Demo section.
• --target=steam: records Steam's Big Picture CEF (theme-loader recolor, Store Bridge Epic collection) — run from Gaming Mode.

Shared CDP/nav machinery extracted to scripts/lib/overlay-cdp.ts; scaffold-plugin-readmes.ts renders a ## Demo section from assets/demo.webp.

Privacy / exclusions (TOUR_SKIP)

Never toured (no tour.json + hard skip): network-info, playtime, bluetooth, storage-cleaner, display-settings, recomp.

Demos in this PR (19 plugins)

tdp-control (hero, in root README) + apex, wifi, storage, input-plumber, disable-controller-input, rgb-control, battery-tracker, lsfg-vk, protondb-badges, quick-links, hltb, steamgriddb, theme-loader, sound-loader, flatpak-manager, store-bridge, launch-options, fan-control — each embedded in its plugin README via ## Demo.

Notes for review

• Footprint: demo clips total ~59 MB committed (WebP, no LFS per discussion). Every clip is tuned to ~2–4 MB; art-heavy library grids (hltb/protondb) run at a lower width to fit.
• wifi and storage are included — they're the "stop WiFi power-saving dropouts" and "mount a lost game drive" fixes, not the privacy-sensitive network-info/storage-cleaner you excluded. Say if you'd rather drop them.
• A few tours flip real device state to demo it (fan-control → Manual/Custom curve, rgb-control → Static, sound-loader → Default pack) — reversible in-app.

Reproduce

bun run capture:videos --tours                    # all plugin tours → videos/review/
bun run capture:videos --promote=<id,…>           # → assets/demo.webp + README

🤖 Generated with Claude Code

[srsholmes]

Parking this as an experiment — the captured tour videos don't look good enough in this format to ship. The tooling works end-to-end (CDP screencast → ffmpeg → captioned WebP, per-plugin tour.json, --tours/--promote, --target=steam), and all the work is preserved on the branch feat/plugin-tour-videos if we want to revisit later (e.g. different format, better framing, or a hosted-video approach). Not deleting the branch.