Spec review (live negative test) found s3-request-presigner unconditionally
unsigns content-type: header-less PUT returns 200, so the previous docblock
claiming signature enforcement was a false guarantee. Content-Type is now
documented as convention-only; head() returns contentType so the complete
step (Task 19) can verify it server-side against the session declaration.
Co-Authored-By: Claude Code <noreply@anthropic.com>
浅念