fix(render): resolve repeated element readiness and props in the row's own scope

[blove]

What was broken

RenderElementComponent rendered each repeat item through a per-item prop context, but computed the mount-readiness gate (notReady) and the mount class (mountClass()) from the NON-repeat prop context. resolveElementProps resolves { $item: … } / { $index: … } / { $bindItem: … } to undefined when the context carries no repeat scope, and isElementReady treats any undefined-valued prop as "still streaming".

So a repeating element whose props are all $item-bound tripped the gate and mounted its fallback (a bare registration means DefaultFallbackComponent) — or nothing at all — for every row, permanently. The diagnosis was confirmed against the code and then reproduced: the new spec file failed 8/8 before the fix, with expected [] to deeply equal ['Alpha', 'Beta', 'Gamma'] and a $bindItem used outside repeat scope: "label" warning from @json-render/core proving readiness ran with no scope.

The streaming demo hid the defect: partial JSON yields props: {} before the $item keys arrive, which reads as ready and latches mountedReal for the whole element. The specs added in #1056 sidestepped it by reading the item from REPEAT_SCOPE instead of binding $item props.

Two adjacent instances of the same root cause were fixed with it:

• ActionBinding.params resolved through this.propCtx(), so { $item: … } params on a repeated element reached the handler as undefined.
• RENDER_HOST was provided once per element, so a component emitting through injectRenderHost() inside a repeat could not say which row fired.

What changed

libs/render/src/lib/render-element.component.ts

• One repeatPropCtxs computed is now the single source for every per-row derivation: props, bindings, readiness, mount class, input filtering, visibility and action params.
• repeatRawNotReady / repeatNotReady / repeatMountClasses are the per-row counterparts of notReady / mountClass. A row shows its fallback while its own props are undefined or fail the entry's Standard Schema, while its ready siblings mount the real component. Fallback behavior for genuinely-undefined props is unchanged.
• The one-way fallback latch is kept per row index — the identity the @for block already tracks — in a second constructor effect, mirroring the existing single-mount latch.
• invokeHandlers(event, payload, repeatIndex?) resolves params in the emitting row's context. repeatInputs hands each row an emit bound to its index, and repeatInjectors provides a row-scoped RENDER_HOST so injectRenderHost().emit(…) behaves identically.
• The mount-evidence telemetry guard dropped its visible()/notReady() precondition and relies on the outlet identity check alone: an element-level readiness flag cannot describe a list whose rows differ. Unknown, hidden, unready and empty-repeat elements are still not reported (covered by the existing development-mount.spec.ts table).

libs/render/src/lib/repeat-scope.spec.ts (new, 8 specs, all failing before the fix)

• an $item-bound prop over an array of objects, and { $item: '' } over strings
• $bindItem resolved through each row's basePath
• fallback shown only for the rows whose props are genuinely undefined
• a registry Standard Schema validated per row
• visible per row alongside $item-bound props (the fix(render): honor every ActionBinding field, per-item visible, real element lifecycle and state paths #1056 feature)
• $item-bound action params, through both the emit input and injectRenderHost()

cockpit/render/repeat-loops — the fix makes the more direct demo possible, so the store now holds [{ label: 'Alpha' }, …] and the repeated element binds { $item: 'label' } instead of { $item: '' } over plain strings. The e2e still asserts the rendered rows and passes unchanged.

Docs: render/guides/repeat-loops.mdx gains a "Per-item readiness" section (per-row gating, per-row schema, per-row action params) and its callout now describes the object array; render/guides/registry.mdx says the fallback switch is one-way per row for a repeating element and that the host is row-scoped inside a repeat; RenderHost's JSDoc says the same, with api-docs.json regenerated.

Verification

• npx nx run-many -t lint,test,build --projects=render,chat --skip-nx-cache — green (0 lint errors)
• npx vitest run --root apps/website --reporter=dot — 137 files, 1382 tests passed
• npx nx run-many -t build for all six cockpit-render-*-angular projects — green
• npx nx e2e cockpit-render-repeat-loops-angular — 3 passed; the other five render e2e suites — 2 passed each
• GROWTH_FORM_POLICY=growth_v1 npx nx build website — green

Not run: nx run render:type-tests — the render project has no type-tests target (only langgraph, chat and ag-ui define one). chat:type-tests fails on this branch and on main alike, with a pre-existing TS5101: Option 'baseUrl' is deprecated error in libs/chat/tsconfig.type-tests.json, untouched here.

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