refactor(push): extract checkFileSize + pin the single-file-cap boundary

[LukasWodka]

Summary

Mutation testing (gremlins) surfaced a real gap: the size > MaxSingleFileBytes single-file-cap guard was duplicated at 4 sites (stream.go, tabular.go, text.go ×2), and its boundary was untestable at every one — MaxSingleFileBytes is a 500 MB const, so > vs >= could only be exercised with a 500 MB fixture. The CONDITIONALS_BOUNDARY mutant survived at all four.

Extract checkFileSize(relPath, size) so the guard lives in one place (behavior-identical — each caller still returns its own arity with the same sizeError), and add a unit test that asserts the boundary at exactly MaxSingleFileBytes with int64 values — no fixture.

Mutation-proven: flipping the helper > to >= fails TestCheckFileSize/exactly_at_cap_is_allowed.

Test plan

• make ci green (build, vet, gofmt -s, go test -race, errcheck/ineffassign/misspell, schema-check).
• Pure refactor + one new unit test; the 4 call sites keep identical behavior.

🤖 Generated with Claude Code

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Note

Low Risk
Behavior-preserving refactor across push validation paths plus a new unit test; no API or cap value changes.

Overview
Centralizes the duplicated size > MaxSingleFileBytes guard into checkFileSize(relPath, size) in walk.go and routes discovery, tabular, text sidecar, and stream-time tar paths through it instead of inline checks. Customer-facing behavior stays the same: over-cap still returns the existing sizeError with the same file path and messaging.

Adds TestCheckFileSize to assert the cap boundary with int64 sizes only—especially that a file exactly at MaxSingleFileBytes is allowed (> not >=)—so mutation testing can catch a >= flip without a 500 MB fixture.

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[LukasWodka]

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[saadqbal]

LGTM 👍 All six call sites are faithful 1:1 extractions (same name + size args, same sizeError), and centralizing the guard finally makes the > vs >= boundary assertable at exactly the cap without a 500 MB fixture. Clean.