Fix RFC 7230 §3.3.3 violation: Transfer-Encoding takes precedence over Content-Length

[Copilot]

When both Transfer-Encoding: chunked and Content-Length headers are present, readResponseBody was checking content_length first — violating RFC 7230 §3.3.3, which mandates that Transfer-Encoding takes precedence and Content-Length must be ignored.

Description

Reorder the checks in readResponseBody so meta.chunked is evaluated before meta.content_length:

// Before (incorrect precedence)
fn readResponseBody(...) ![]const u8 {
    if (meta.content_length) |cl| { ... }  // checked first — wrong
    if (meta.chunked) { ... }

// After (RFC-compliant)
fn readResponseBody(...) ![]const u8 {
    if (meta.chunked) { ... }              // Transfer-Encoding wins per RFC 7230 §3.3.3
    if (meta.content_length) |cl| { ... }

Added a /// doc comment citing the RFC so the ordering intent is self-documenting.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring
• Performance improvement
• Test addition/modification
• CI/CD changes

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Testing

• Unit tests

Additional Notes

This is a correctness fix for an edge case (server sending both headers). Docker's own API is well-behaved, but the fix ensures correct behaviour against any RFC-conformant or buggy intermediary.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.