Add PosterBoard: FigJam-style pan/zoom board card (v1 step 1)

[burieberry]

Adds poster-board/, step 1 of the minimal poster-board plan (CS-12193): an infinite-canvas board card with pan, zoom, and a zoom toolbar — no cards on the board yet (that's step 2).

Closes CS-12213.

What's here

• rig.gts — pure-TS pan/zoom camera engine ("rig" as in camera rig): cursor-anchored wheel/pinch zoom, drag-pan sessions with velocity sampling, rAF momentum with time-normalized inertia decay for both pan and zoom. No DOM or card-api dependencies; ported nearly verbatim from the experiments-realm prototype.
• poster-board.gts — the PosterBoard card def. Isolated view wires pointer/wheel events into the rig and renders from its tracked state: single scale() translate() transform on one plane element, dot grid, zoom HUD (+ / % / − / 100% / Fit), Shift+=/−/0 keyboard zoom. Fit currently resets the view; real fit-to-content lands in step 4 (CS-12216).
• poster-board.test.gts — live tests (3 tests / 8 assertions): isolated render + toolbar + computed cardTitle, zoom buttons changing/resetting the zoom readout, Fit resetting the view.
• PosterBoard/demo-poster-board.json — a demo instance.
• README.md — how to run the tests (browser and headless).

Conventions applied

Semantic HTML (h1/p/header, role='toolbar', <output> readout, aria labels), semantic color tokens only with bg/foreground pairing (HUD is a --card surface; color-mix for translucency — zero hex), local --pb-* custom properties for all metric values, htmlSafe getters for the dynamic transform/cursor styles, data-test-* attributes last on each element, and full teardown in willDestroy (momentum loops + window listener).

Testing

The live-test CI job does not run on catalog-only PRs (its path filter excludes this repo's mount point), so tests were run locally against a running dev stack via the QUnit live-test page filtered to poster-board:

3 tests completed in 903 milliseconds, with 0 failed, 0 skipped, and 0 todo.
8 assertions of 8 passed, 0 failed.

ESLint, ember-template-lint, and glint (ember-tsc) all pass for contents/poster-board/.

🤖 Generated with Claude Code

[github-actions]

Staging Submissions Preview

This PR's content is pushed to the staging submissions realm: https://realms-staging.stack.cards/submissions/

Changed folders:

• poster-board/

Updated at 2026-07-17 20:07:45 UTC for commit 2a53765. Shared realm: only this PR's changed files are pushed; files touched by multiple PRs reflect whichever pushed last, and deleted files are not removed.

[burieberry]

[Claude Code 🤖] Superseded by #666 — same commits; the head branch was renamed from cs-12193-productionize-poster-board to cs-12213-posterboard-step-1-live-test-for-panzoom-board-first-boxel to match the step-1 ticket, which auto-closed this PR.