feat(studio): sourcePatcher data-hf-id targeting (R1, T3)

[vanceingalls]

What

Adds hfId as a first-class target field to sourcePatcher (packages/studio/src/utils/sourcePatcher.ts). When target.hfId is set, the patcher finds the element via [data-hf-id="${hfId}"] before falling back to id or CSS selector.

Also tightens the existing id= regex patterns with a negative lookbehind to prevent false matches on attributes like data-id= or composition-id=.

Why

T3 spec — the sourcePatcher path handles the studio's in-browser rich-text editing. It needs to accept hfId targets so the studio can address elements by stable content-based id (R1) rather than a positional CSS selector that can drift when siblings are inserted. Depends on PR #1270.

How

• hfId?: string added to the patch target type
• Target resolution order: hfId → id → selector
• [data-hf-id] lookup uses the same attribute-selector pattern as sourceMutation
• Negative lookbehind fix: (?<!\w)id= prevents data-id= from matching id-based patterns

Test plan

• T3 spec tests in sourcePatcher.test.ts — hfId targeting cases pass
• All pre-existing sourcePatcher tests pass (no regressions)

[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 👈 (View in Graphite)
• feat(core): clip-model hf- ids minted at parse, emitted as data-hf-id (R1) #1270
• feat(core): ensureHfIds node-id pass + shared hf- mint helper (R1) #1269
• main

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