feat(core): clip-model hf- ids minted at parse, emitted as data-hf-id (R1)

[vanceingalls]

What

Wires ensureHfIds (PR #1269) into parseHtml so every parsed composition gets stable data-hf-id attributes before the element model is built.

Clip model id chain:

const id = el.getAttribute("data-hf-id") || el.id || `element-${++idCounter}`;

data-hf-id is now the primary identity; existing HTML id attrs and the counter fallback are preserved for backwards compatibility.

Bridge for legacy callers: updateElementInHtml and removeElementFromHtml in htmlParser.ts now try [data-hf-id="${id}"] when getElementById fails, so string-based callers that pass a hf-xxxx value continue to work without knowing about the new field.

Why

Without this PR, ensureHfIds is a no-op — the helper exists but nothing calls it. This is the commit that makes T2 tests turn green and makes every parseHtml call produce stable hf- ids. Depends on PR #1269.

How

// before DOMParser.parseFromString:
const withIds = ensureHfIds(html);
const doc = parser.parseFromString(withIds, "text/html");

htmlParser.ts baseline snapshots updated to reflect the hf- id format (see 168c0452c).

Test plan

• T2 spec: 3 previously-.fails tests now pass — elements get hf- prefixed ids, format matches /^hf-[a-z0-9]{4}$/, adding a sibling doesn't change existing ids
• All pre-existing htmlParser.test.ts baselines updated and passing
• Existing stableIds.test.ts baselines (round-trip, uniqueness, existing-id preservation) still green

[vanceingalls]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(core): sourceMutation data-hf-id targeting (R1, T7) #1272
• feat(studio): sourcePatcher data-hf-id targeting (R1, T3) #1271
• feat(core): clip-model hf- ids minted at parse, emitted as data-hf-id (R1) #1270 👈 (View in Graphite)
• feat(core): ensureHfIds node-id pass + shared hf- mint helper (R1) #1269
• main

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