refactor(player-core): drop svelte for a signals-based dom layer, upgrade to TypeScript 7

[AbianS]

Summary

Four commits:

1. build: share dependency versions through pnpm catalogs: shared dependencies (TypeScript, React, Tailwind, the Vite/Vitest/size tooling) live in named catalogs in pnpm-workspace.yaml.
2. refactor(player-core): replace svelte with a signals-based dom layer: the player no longer ships or depends on a UI framework.
3. build: upgrade to typescript 7: TypeScript 7 everywhere except player-vue, which stays on 6.
4. chore(player-core): replace dist import check with a lint rule: the alien-signals import guard moves from a post-build script to a Biome rule.

player-core without Svelte

The player is embedded in other people's apps, so it shouldn't make them install or download a framework runtime. The Svelte runtime was about half of the player's weight.

• src/dom/: a small DOM layer over alien-signals. h()/svg() create elements, and a function prop or child stays bound to the signals it reads (one effect per binding, nothing re-renders). show() handles conditional views with exit animations, each() keyed lists, mount() scoped disposal, and batch() grouped writes.
• src/ui/<Component>/: the seven components as plain functions, each with its CSS in <Component>.styles.ts. Selectors are scoped under .openshowcase-player and keyframes prefixed with openshowcase-, and the CSS is injected when the component is created, never at import time.
• src/core/: unchanged. The public API (new Player({...}).mount(), next(), goTo(), destroy()…) is the same, so the adapters and the extension needed no changes.

Build and output

• Build: Rslib in bundleless mode replaces Vite + dts-bundle-generator. dist/ has one readable, unminified ESM file per module (the host app minifies), declarations from tsc, and "sideEffects": ["**/*.css"]. Tailwind ships as dist/app.css.
• alien-signals is a devDependency compiled into dist/dom/signals.js: the published package depends on nothing but the schema. Only src/dom/signals.ts may import it, and a Biome noRestrictedImports rule enforces that: a direct import would stay in dist/ as an import of a package the published package doesn't declare.
• size-limit now measures what a host ships (bundled and minified by esbuild), with a second budget that fails if the player stops tree-shaking away from the tooltip geometry.

What a host ships (minified, brotli)	Before	After
Player (JS + CSS)	~26 KB	14.7 KB
Tooltip geometry only (the extension editor)	5.6 KB, plus the player's CSS injected	0.75 KB
Runtime dependencies	svelte	none

How it was verified

• Same specs on both versions: during the migration, every component test and the player integration suite ran against both the Svelte and the new implementation (198 tests).
• Rendering parity: each component, and the whole player step by step in light and dark themes, was compared against the Svelte original: normalized DOM plus the browser's computed styles. Deliberately breaking a style or class made those checks fail, so they weren't passing by accident.
• Real demo: a real recorded demo (video, zoomed photos with hotspots, a zoomed video) played end to end in headless Chromium through the built package, with no console errors.
• After removing Svelte: the specs run on the new implementation only (140 tests). The parity scaffolding was removed along with it.

TypeScript 7

• catalog:core → typescript 7.0.2. tsc is the native compiler, and Rslib generates declarations with it (tsgo).
• player-vue stays on 6 through a new catalog:vue-tooling, like nest-cli in contapro: vue-tsc and the Vue SFC loader load TypeScript's JS API, which 7 removed.
• Tooling: player-core no longer uses dts-bundle-generator, the other API-bound tool.

Checks

biome ci, build, check-types, size (all 17 tasks) and every package's tests pass: player-core 140, extension 119, schema 27, exporter 8.

No changeset: it will be added later with the other pending changes.