fix(smrt-core): prefer huggingface transformers for embeddings

[willgriffin]

Summary

• prefer @huggingface/transformers for local embeddings when available, with fallback to @xenova/transformers
• preserve non-module runtime failures and improve the missing-package error message
• add regression coverage for the module resolution behavior

Verification

• pnpm --filter @happyvertical/smrt-core exec vitest run src/tests/embedding-provider-transformers-resolution.test.ts
• pnpm --filter @happyvertical/smrt-core exec tsc --noEmit
• pnpm --filter @happyvertical/smrt-core build

[Copilot]

Pull request overview

This PR updates @happyvertical/smrt-core local embedding initialization to prefer @huggingface/transformers (when installed) and fall back to @xenova/transformers, while improving missing-package errors and adding regression tests for module resolution behavior.

Changes:

• Add runtime resolution logic to prefer @huggingface/transformers for local embeddings with fallback to @xenova/transformers.
• Improve the “missing optional dependency” error message and preserve non-module runtime failures.
• Add Vitest coverage for the package resolution order and error behavior.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pnpm-lock.yaml	Adds @huggingface/transformers to core dev deps (lockfile needs to be consistent with package.json).
packages/core/src/embeddings/provider.ts	Implements optional transformers package resolution and uses it for local pipeline initialization and availability checks.
packages/core/src/tests/embedding-provider-transformers-resolution.test.ts	Adds regression tests for preference order, fallback, and error propagation.
packages/core/package.json	Declares @huggingface/transformers as an optional peer dependency and adds it to devDependencies.
.changeset/fair-squids-tickle.md	Patch changeset documenting the behavior change and Node 24/sharp motivation.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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[Copilot]

In the lockfile, packages/core still pins @types/node to 24.10.9, but packages/core/package.json specifies @types/node: "25.0.9". Please regenerate/update pnpm-lock.yaml so the recorded specifier/version matches the package.json dependency set (usually by running pnpm install from the repo root).

[Copilot]

The final if (lastError) { throw ... } followed by an unconditional throw ... is redundant here, since both branches throw the same error. Consider removing the conditional (and potentially the unused lastError tracking) to simplify the control flow.