refactor(errors): separate ServerApiError from RequestError

[JuroUhlar]

• Add ServerApiError extends RequestError, thrown for structured Server API error responses; it carries the strongly typed errorCode (ErrorCode) and responseBody: ErrorResponse.
• TooManyRequestsError now extends ServerApiError.
• RequestError becomes the base for request-level errors, thrown directly for non–Server-API responses (e.g. an intermediate proxy). It no longer declares errorCode.
• Export the ErrorCode type; consolidate the error-handling changeset into one entry.
• Remove the base branch's LooseAutocomplete/typeUtils.ts, now superseded (see below).
• Readme error-handling section updated to show ServerApiError/ErrorCode narrowing.

Supersedes the base's LooseAutocomplete approach

Base #251 kept errorCode on RequestError, widened to LooseAutocomplete<ErrorCode> with a statusText placeholder on the proxy path. This PR instead moves errorCode to ServerApiError only (strictly typed), so RequestError has no errorCode at all. That makes LooseAutocomplete dead code, so it's removed here, and the two error changesets are folded into one coherent entry.

Because this PR reverses part of its base, the stack is only coherent if #251 and this PR merge together. If #251 releases on its own first, we'd ship LooseAutocomplete and then remove it. Consider collapsing the stack (or trimming #251 down to just the ErrorCode export) before merging.

Discussion point: minor vs major

On the non–Server-API (proxy) path, errorCode previously reflected response.statusText; it is now absent (undefined). The compiler can't catch this for untyped consumers, so it's a runtime change, not just a type change — flagging against the repo's "runtime API follows semver strictly" note. Shipped as minor; happy to bump to major if preferred.

Discussion point: class name

Named ServerApiError (vs the previous ApiError) to contrast with RequestError and make the "structured Server API error" meaning explicit. Easy to revert to ApiError if preferred.

[changeset-bot]

🦋 Changeset detected

Latest commit: a639fae

The changes in this PR will be included in the next version bump.

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Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	100%	356/356
🟢	Branches	100%	126/126
🟢	Functions	100%	36/36
🟢	Lines	100%	356/356

Test suite run success

81 tests passing in 24 suites.

Report generated by 🧪jest coverage report action from a639fae

Show full coverage report

St	File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
🟢	All files	100	100	100	100
🟢	src	100	100	100	100
🔴	...edApiTypes.ts	0	0	0	0
🟢	index.ts	100	100	100	100
🟢	sealedResults.ts	100	100	100	100
🟢	...rApiClient.ts	100	100	100	100
🟢	types.ts	100	100	100	100
🟢	urlUtils.ts	100	100	100	100
🟢	webhook.ts	100	100	100	100
🟢	src/errors	100	100	100	100
🟢	apiErrors.ts	100	100	100	100
🟢	...orResponse.ts	100	100	100	100
🟢	toError.ts	100	100	100	100
🟢	unsealError.ts	100	100	100	100

[github-actions]

🚀 Following releases will be created using changesets from this PR:

@fingerprint/node-sdk@7.5.0

Minor Changes

• Separate Server API errors from other request errors and strongly type the error code.

  • Added ServerApiError (extends RequestError), thrown when the Server API returns a structured error response. It exposes a strongly typed errorCode (ErrorCode) and responseBody: ErrorResponse.
  • Exported the ErrorCode type (the union of error codes returned by the Fingerprint Server API).
  • TooManyRequestsError now extends ServerApiError.
  • RequestError is now the base class for request-level errors and is thrown directly for non–Server-API responses (for example, errors returned by an intermediate proxy). It no longer declares errorCode.

  Migration: ServerApiError extends RequestError, so error instanceof RequestError checks keep working. To read the error code, narrow to ServerApiError (if (error instanceof ServerApiError) { error.errorCode }).

  Runtime note: on the non–Server-API (proxy) error path, errorCode previously reflected response.statusText; it is now absent (undefined). This is a runtime change for untyped consumers that read errorCode on such errors, not merely a type change. (a639fae)

Patch Changes

• errors: Normalize caught values into real Error instances, so errors from unseal and JSON parsing always carry a genuine Error. (5764c11)