Handle open-ended byte ranges and empty list members correctly

[OskarEichler]

Summary

Accept valid open-ended byte ranges starting at zero, ignore empty list members, and serialize 0..-1 as bytes=0-. Keep rejecting a sole zero-length suffix and reject empty exclusive Ruby ranges before decrementing their end.

Reproduction

With r = Net::HTTP::Get.new('/'), r['Range'] = 'bytes=0-'; r.range raises before the patch but returns [0..-1] afterward. r.range = 0..-1 previously produced bytes=-0. Parsing bytes=,0-1 or bytes=0-1,,2-3 also raised. Assigning 0...0 previously produced an invalid range.

Verification

• Ruby 4.0.6 through rbenv; existing bundle exec rake test: 201 tests, 914 assertions, zero failures/errors, both baseline and this isolated patch.
• 26 focused checks cover open-ended/suffix/multiple ranges, empty list members, invalid descending ranges and empty exclusive assignments. HTTP list recipients ignore empty members: RFC 9110 section 5.6.1.2.
• Ruby syntax and git diff --check pass. Supplemental Lint scan retains the same 25 pre-existing findings; no new findings by file/cop.
• No test/spec files were added or modified, per this contribution's explicit no-new-tests constraint. Focused reproductions were run externally.

Compatibility and limitations

No API or dependency change. Intentional corrections: these valid inputs now succeed; assigning an empty exclusive range raises Net::HTTPHeaderSyntaxError. Sole bytes=-0 remains rejected.

Based on master 23e859e92e10e43cad520fcacac3fd43640dba7b. Optional external OpenSSL tests and other Ruby/OS combinations were not run. Existing related issues/PRs were checked; this is a focused correctness change, not a claim of exhaustive coverage.

Reference: https://www.rfc-editor.org/rfc/rfc9110.html#section-5.6.1.2