fix: send multipart content_type before the file part on asset upload

[wei-hai]

Asset upload against public-api failed with:

422 invalid_body: content_type is required and must be sent before the file field

public-api streams the multipart upload and needs content_type (and the other metadata fields) to arrive before the file part so it can route the file stream without buffering. postAssets appended file first.

Fix: append the metadata fields (content_type, file_path, expected_hash, tags) first and file last. The stub server now rejects a file-before-content_type body (mirroring public-api), so the existing postAssets tests guard against a regression. vitest 112/112, tsc/oxfmt/hygiene clean.

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Reviewing files that changed from the base of the PR and between f672d36 and 60a8cc1.

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• src/low/errors.test.ts
• src/low/errors.ts

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📝 Walkthrough

Walkthrough

postAssets now sends multipart metadata before the file. The test stub validates this ordering, and a transport test confirms correctly ordered uploads succeed.

Changes

Asset upload multipart ordering

Layer / File(s)	Summary
Multipart ordering and validation src/low/transport.ts, test/support/stub-server.ts, src/low/transport.test.ts	postAssets appends metadata before file; the stub returns 422 invalid_body when content_type is missing or follows file; the test verifies a successful upload and one recorded request.

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@test/support/stub-server.ts`:
- Around line 390-393: Update the multipart ordering validation around the body
field searches to inspect only parsed multipart Content-Disposition field names,
not arbitrary body content. Extract the ordered headers with a multipart parser
or equivalent and enforce that the file field precedes content_type only when
those actual fields are present, preserving the existing malformed-request
rejection behavior.

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Configuration used: Organization UI

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Run ID: 16107771-8b44-4141-91da-185565a94985

📥 Commits

Reviewing files that changed from the base of the PR and between bdb7bbb and f672d36.

📒 Files selected for processing (3)

• src/low/transport.test.ts
• src/low/transport.ts
• test/support/stub-server.ts