fix(ui): forward forceRender into CollapsibleField's nested RenderFields

[okxint]

What

Closes #17473

CollapsibleField receives forceRender from the field dispatcher (RenderField.tsx) but never destructures or forwards it — it's silently dropped before reaching the nested <RenderFields> call.

Why it matters

Without forceRender, each nested field is wrapped in RenderIfInViewport, which defers rendering until an IntersectionObserver reports the element as visible. Browsers suspend IntersectionObserver callbacks when document.hidden is true (backgrounded tabs, embedded webviews, visibility-throttled automation). So hasRendered stays false indefinitely and the collapsible's children never appear — no error, no warning.

DocumentFields explicitly passes forceRender: true for a document's own fields (at both the main and sidebar call sites), intending that field trees are never subject to lazy viewport-gated rendering. Row, Tabs, and Array already honor this by forwarding the prop; Collapsible was the only container type that didn't.

Fix

Two lines, mirroring the existing pattern in Row/index.tsx:

+    forceRender = false,
     indexPath,

           <RenderFields
             fields={fields}
+            forceRender={forceRender}

Verification

# Confirm the prop was absent before
grep -rn "forceRender" node_modules/@payloadcms/ui/dist/fields/Collapsible/
# (no output)

# Confirm Row already does this correctly
grep -n "forceRender" packages/ui/src/fields/Row/index.tsx
# 17:    forceRender = false,
# 34:          forceRender={forceRender}