chore(fast-html): use @microsoft/fast-build to build slotted fixture

[janechu]

Pull Request

📖 Description

Adds the slotted test fixture to @microsoft/fast-html and generates its index.html using @microsoft/fast-build, consistent with the other fixtures (attribute, binding, event).

The slotted fixture covers f-slotted attribute directives, which bind references to slotted child nodes in a FAST template (e.g. <slot f-slotted="{slottedNodes filter elements()}"></slot>). Because f-slotted is client-side only, @microsoft/fast-build strips it from the rendered Declarative Shadow DOM while preserving the data-fe-c hydration binding count so the FAST runtime can allocate the correct number of binding slots.

The fixture exercises three slot configurations:

• Default slot with element filter: f-slotted="{slottedNodes filter elements()}"
• Named slot with no filter: <slot name="foo" f-slotted="{slottedFooNodes}">
• Named slot with element type filter: <slot name="bar" f-slotted="{slottedBarNodes filter elements(p, ol)}">

🎫 Issues

No open issues directly addressed.

📑 Test Plan

• npm run build:fixtures in packages/fast-html runs cleanly and regenerates slotted/index.html — f-slotted directives are stripped from shadow DOM output, data-fe-c binding annotations are preserved on each slot.
• All other fixture outputs (attribute, binding, event) are unchanged.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

⏭ Next Steps

• Add a Playwright spec file (slotted.spec.ts) covering hydration of the f-slotted fixture to verify client-side slotted node reference assignment after SSR.

[Copilot]

Pull request overview

Adds a new slotted test fixture to @microsoft/fast-html and wires it into the existing @microsoft/fast-build-based fixture build pipeline so its index.html is generated consistently with the other fast-build fixtures.

Changes:

• Added slotted fixture inputs (entry.html, templates.html, state.json) and generated output (index.html).
• Updated packages/fast-html/scripts/build-fixtures.js to include slotted in the fixtures built via @microsoft/fast-build.
• Added a Beachball change file documenting the chore-level update.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/fast-html/test/fixtures/slotted/templates.html	Defines f-slotted usages to exercise default and named slot configurations with filters.
packages/fast-html/test/fixtures/slotted/state.json	Provides the fixture state input for the fast-build CLI (empty object).
packages/fast-html/test/fixtures/slotted/index.html	Generated HTML output showing f-slotted stripped from DSD while preserving data-fe-c-* hydration bindings.
packages/fast-html/test/fixtures/slotted/entry.html	Entry HTML used as input to build the fixture output via fast-build.
packages/fast-html/scripts/build-fixtures.js	Adds slotted to the fast-build fixture build list.
change/@microsoft-fast-html-slotted-fdec5a05-d62e-45dd-92a7-e47213d20812.json	Records the change in the repo’s change management system (Beachball).