fix(cms): resolve site globals in resolveDecoPage, replacing tanstack side path (#292)

[JonasJesus42]

Context

Closes #292.

Since v6.7.4, resolveSiteGlobals() ran unconditionally on every CMS route via a
tanstack-only path bolted onto loadCmsPage/loadCmsHomePage, injecting the CMS
Site block (theme + global + pageSections) into every page. This diverged
from how the old framework (deco-cx/apps website + deco-cx/deco) handled globals.

Approach — replicate the old-deco model (faithful, no opt-out flag)

Old deco declared theme + global on the website app and prepended them in the
shared Page loader, resolved through the one resolution engine. We mirror that:

• packages/blocks (runtime): resolveDecoPage now prepends the Site block's
  theme + global (opt-in by declaration) into page.resolvedSections, deduped
  so page sections win, resolved via the normal path reusing resolvedLayoutCache.
  site.pageSections is intentionally dropped (old deco's Site block never had it —
  it was the divergence behind Breaking change (6.7.4): resolveSiteGlobals() now runs on all CMS routes, silently activating site globals for sites not using withSiteGlobals() #292).
• packages/tanstack: cmsRoute stops calling resolveSiteGlobals() + the
  manual merge/dedupe; drops the unused siteGlobals.rawRefs return. withSiteGlobals()
  stays a deprecated no-op. The __nav: client-nav dedup bucket (Client-side navigation renders blank for deferred sections that depend on per-request app context (admin-source-of-truth deferral leaks into SPA nav) #277) is preserved.
• packages/nextjs: no code change — it renders page.resolvedSections, so it
  now picks up declared globals through the same path (unifies both bindings).

Breaking change

Declared theme/global render on every page (as in 6.7.4+ and old deco); a site
with a malformed Theme must fix it site-side. site.pageSections no longer injected.
Heads-up filed at deco-sites/lebiscuit-tanstack#143.

Tests

+5 targeted tests in resolve.test.ts (prepend order, dedupe, opt-in, Site/site
key casing). Full suites pass: blocks 1072, tanstack 107, next 39. blocks typecheck clean.

🤖 Generated with Claude Code

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Summary by cubic

Moves site globals resolution into the runtime: resolveDecoPage now prepends Site.theme and Site.global to every page and removes the tanstack-only globals path, fixing the divergence in #292. This unifies behavior across @decocms/tanstack and @decocms/nextjs and dedupes against page sections.

• Refactors

  • @decocms/blocks: resolveDecoPage gathers site.theme + site.global, resolves them with the same path and layout cache, and prepends them; drops site.pageSections as a globals source; dedupes so page sections win.
  • @decocms/tanstack: cmsRoute no longer calls resolveSiteGlobals() or merges globals; removes siteGlobals.rawRefs from loader return; withSiteGlobals() kept as a deprecated no-op.
  • Opt-in by declaration; works for SSR and SPA with one consistent path.

• Migration

  • Declare globals under site.theme and site.global; stop relying on site.pageSections being injected.
  • Ensure your Theme is valid, as it now renders on every page.
  • Remove or update any direct uses of resolveSiteGlobals()/withSiteGlobals(); prefer the runtime path via resolveDecoPage.

^{Written for commit 42131f4. Summary will update on new commits.}