docs: embed instructional video clips across Cloud pages

[nellins]

What

Embeds eight instructional video clips across the Cloud docs — muted, autoplaying, looping MP4s recorded by Drew in Screen Studio and cut in the bm-video Remotion pipeline (title cards, caption pills, instructional pacing).

Page	Clip(s)
start-here/quickstart-cloud	Meet your workspace (2:53 intro)
cloud/note-editor	Editing modes · Frontmatter · Command palette
cloud/comments-and-suggestions	Suggest edits → AI reviews them (two-act)
cloud/mcp-app	Pocketbook full tour
cloud/themes	Theme picker + dark mode
cloud/web-app	Import flow (in the Import data section)

How

• New VideoLoop content component (app/components/content/VideoLoop.vue) mirroring ThemeImage — same border/rounding, autoplay loop muted playsinline preload="metadata".
• Videos in public/videos/, H.264 CRF 24 faststart, 63MB total (largest: quickstart 17MB).
• Purely additive: branch cut from freshly-pulled main (7f54c75); only inserted lines in the six content files — no existing text or media touched. Existing screenshots kept alongside the clips.

Verification

• npm run check:docs passes (pre-existing warnings only).
• Rendered locally on all six pages; embeds confirmed serving on each route.

Review notes for Paul

• 63MB of video in git is the one design smell — happy to move these to object storage/CDN and reference by URL if you'd rather keep the repo lean; the component wouldn't change.
• The demo content is the fictional Lighthouse studio workspace + a fresh onboarding account. One known blemish accepted by Drew: the import clip's Activity panel briefly shows internal entry titles (~0:38–0:41).

🤖 Generated with Claude Code

[nellins]

Added in 72ac0b6 at Drew's request: the what-is-basic-memory page's explainer embed now serves the current hero video (v30) from this repo (public/videos/hero.mp4, 8.5MB, audio kept since the player has controls) instead of the old basicmemory.com/videos/explainer-video.mp4. Same :video embed pattern, one-line src swap — the only non-additive line in this PR, and it's a deliberate content replacement Drew asked for.

[nellins]

Follow-up per Drew's review of the embeds: autoplay and looping are gone — videos now present as their title-card poster with full controls (play, scrub, fullscreen). Component renamed VideoLoop → DocsVideo accordingly; poster frames added under public/videos/posters/ (544KB total).

[nellins]

Heads-up for review: this branch now also carries Drew's product-naming change — Interactive MCP App → Pocketbook throughout (33 refs, 11 pages, titles/nav included). Slugs left unchanged to avoid breaking links; if you want the URLs renamed too that needs redirects and can be a follow-up.