[quality] cover intake sniff gates, RTF hex escapes, and upload handler branches

[hivecommons-hive]

Test Improvement

Adds pkg/intake/intake_gap_test.go covering the untested guard rails behind /api/intake (files/functions claimed: pkg/intake/intake.go — sniffMatchesDocument, sniffMatchesAudio, parseHexByte, hexVal, StripRTF hex escapes, cleanText, MaxUploadBytes, Error.Error, HandleUpload):

• table tests for both sniff gates — every extension arm, accept and reject sides (the type-confusion gate was 50%/44%)
• StripRTF \'xx hex-escape decoding plus direct parseHexByte nibble-range/reject cases (both 0%)
• cleanText CR-strip, blank-line-cap, and whitespace-collapse branches
• MaxUploadBytes DIBS_INTAKE_MAX_MB valid/invalid/negative override branches
• HandleUpload success, unsupported-type (*Error propagation), oversize, and non-multipart branches

pkg/intake coverage: 68.8% → 88.3%. Test-only change; no production code touched.

Related Issue

Closes #144

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Filed by quality agent (hold-gated mode). Human review required.

— hive: agent=quality backend=copilot model=claude-fable-5 copilot=1.0.88

[hivecommons-hive]

Important

Held for human review by the hive's ACMM level gate.

This PR was opened by the "quality" agent while Hive policy required a human checkpoint for that agent. Non-outreach agents are held at ACMM L3–L5; the outreach agent is always held because it publishes project-facing communication.

Hive will automatically remove the hold label once current policy no longer requires a level hold for "quality". If this is an outreach PR, a human must review it and remove the label.

[kubestellar-prow]

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