fix: client data provider falls back to HTML extraction for SSG hosts

[jonlaing]

Summary

Fix client-side navigation on SSG (static-file-hosted) sites — clicking a <Link> updated the URL but blanked the <Outlet>, with no error in the console.

Root cause

makeClientLayer's data provider was doing:

```ts
const response = yield* Effect.tryPromise(() => fetch(`${path}?${qs.toString()}`));
const json = yield* Effect.tryPromise(() => response.json());
return json as unknown as RouteDataService;
```

That works against the SSR HTTP handler (which returns JSON for `?_data=1` requests). It silently breaks on any static host — static file servers ignore the query string and return the target page's HTML shell. `response.json()` throws on that HTML, `.pipe(Effect.orDie)` converts the failure into a defect and kills the fiber. The Outlet's data effect dies before rendering; the URL has already updated because `pushPath` runs before the fetch.

No error surfaces because the fiber's defect is swallowed by the ambient runtime.

Fix

The provider now inspects the response's `Content-Type` header:

• `application/json` — parse as before (SSR server case).
• Anything else — treat as an SSG HTML shell. Extract the `window.EFFEX_DATA` blob that `generateDocument` embeds in every SSG'd page and `JSON.parse` it.

The escapes `serializeForHtml` emits (`\u003c` / `\u003e` / `\u0026`) are native JSON escapes, so the extract → `JSON.parse` round-trip is lossless — including payloads that contain `</script>` or ampersands.

Callers

No config change required. Projects using `Platform.makeClientLayer(router)` just start navigating correctly after upgrading.

Test plan

• 5 unit tests in `Platform.test.ts` covering the extract:
  • Round-trip with `generateDocument`'s real output
  • Payloads containing `<script>`, `</script>`, ampersands
  • No-data-present case → `undefined`
  • Malformed-JSON case → `undefined`
  • Sanity check that `serializeForHtml` produces the expected `\uXXXX` escapes
• Full suite: 733 pass / 2 skipped
• `npx tsc --noEmit` clean
• Manual: verify on the portfolio site that link clicks now render the target page

Note

Two knobs I considered but didn't touch:

1. `.pipe(Effect.orDie)` on the provider effect. This is why the failure was silent. Kept as-is because with the HTML fallback the effect no longer fails in the common case; a genuine network failure still deserves to die.
2. Emit static `?_data=1` JSON files during `buildStaticSite`. Would avoid the HTML round-trip and shave payload size. Bigger change and portable-across-hosts is the more important property right now.

🤖 Generated with Claude Code

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