fix(atproto-comments): ship a Svelte-external build to fix hydration crash (#7)

[Theo-Steiner]

Fixes #7.

Root cause

@svebcomponents/atproto.comments's client build bundled its own Svelte runtime. In a SvelteKit/Vite app — which has its own Svelte — that put two Svelte runtimes on the page. Under experimental.async, the app's async-boundary hydration (#hydrate_resolved_content → legacy-client) crossed into the component's separate runtime and dereferenced a null effect:

TypeError: Cannot read properties of null (reading 'f')

The correctly server-rendered thread was then wiped on the client, leaving only the header. The crash only surfaced through the async wrapper path (the documented self-fetch SSR tier), which is why smaller/synchronous setups didn't hit it.

Fix

The build already supports a Svelte-external variant (@svebcomponents/build ≥ 0.3.1: externalSvelte + pluginDedupe + the hydration-host bundling); this component just never opted in.

• package.json — declare a svelte export condition on . and ./ssr, pointing at new dist/client-svelte / dist/server-svelte builds.
• svebcomponents.config.ts — emit those Svelte-external variants and apply the vendored direct-props HydrationHost to every build variant (matched by outDir/entry, not array index).

Bundler consumers (SvelteKit, Vite) resolve the svelte condition and dedupe the component onto the app's single Svelte runtime, so the crash is gone by construction — there is only one runtime, so there is no cross-runtime effect to corrupt. The default dist/client (Svelte bundled) is unchanged and still serves the CDN / bare-import drop-in, which has no app Svelte to dedupe against.

Verification

• Component: client-svelte/server-svelte externalize Svelte; the vendored host is compiled into every variant; test (11), svelte-check (0 errors), publint, and eslint all pass.
• Real consumer (new-theosteiner.de, the reporter's app, tested via a packed tarball): the duplicate runtime is eliminated — the optimized component dep went from 2 bundled-runtime markers to 0 and now imports the app's shared runtime-*.js chunk. The page still hydrates: 227 → 227 comments, zero page errors.
• Workspace host app: existing hydration e2e still passes.

Consumer follow-up

After publish, consumers just pnpm update @svebcomponents/atproto.comments — no app changes, and any ssr.noExternal entry for this component can be dropped.

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