feat: add NextLabel and Question.Labels

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Summary

• NextLabel(name string, offset int) (next int, end bool): a drop-in for dns.NextLabel on names this package produces — EDM's setQuestionLabels loop keeps its shape and drops the import. dnswire controls the escaping (dots inside labels are always \.), so a forward scan that skips escape sequences replaces miekg's backslash-parity backtracking. Offset must be a label start.
• Question.Labels: range-over-func iterator built on NextLabel, yielding labels in presentation form without dots; the root yields nothing.

Supersedes #10, which GitHub closed when its stacked base branch was merged and deleted.

Verification

• Unit tests: TestNextLabel walks empty, root, plain, escaped-dot, escaped-backslash and \DDD names step by step; TestQuestionLabels covers the iterator including early break. Coverage stays 100% under -race.

• Differential harness: every decoded name is split with dns.NextLabel, and at each label start dnswire.NextLabel must return the same (next, end) — 200k deterministic messages agree.

• BenchmarkLabels (ns/op, zero allocs everywhere):

  name	dnswire.NextLabel loop	dns.NextLabel loop	Question.Labels
  www.example.com.	7.27	8.71	9.51
  a\.b.\000\255x.example.	9.12	11.00	10.82

Summary by CodeRabbit

• New Features
  • Added label iteration for DNS question names in presentation format.
  • Added a helper for advancing through labels while correctly handling escaped dots and trailing dots.
• Documentation
  • Expanded the README with guidance on label iteration and compatibility with the miekg/dns equivalent.
• Tests
  • Added coverage for root, escaped, ordinary, and partially iterated names.
  • Added differential validation and benchmarks across label-processing implementations.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: d0bb89fb-b5aa-46ef-b297-20c6d349fb40

📥 Commits

Reviewing files that changed from the base of the PR and between 2157559 and bcb11f2.

📒 Files selected for processing (5)

• README.md
• benchmarks/benchmark_test.go
• benchmarks/differential_test.go
• dnswire.go
• dnswire_test.go

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The PR adds Question.Labels and NextLabel for presentation-form DNS label parsing. It documents the APIs, adds unit tests, compares results with miekg/dns, and benchmarks three label-splitting implementations.

Changes

Domain label iteration

Layer / File(s)	Summary
Label iteration API dnswire.go, dnswire_test.go, README.md	Question.Labels yields labels without allocation and supports early termination. NextLabel handles escaped content, offsets, and terminal labels. Tests cover root, ordinary, escaped, and octal-escaped names. The README documents both APIs.
Cross-implementation validation benchmarks/differential_test.go, benchmarks/benchmark_test.go	Differential checks compare label sequences and offsets with miekg/dns. BenchmarkLabels compares Question.Labels, dnswire.NextLabel, and miekg/dns NextLabel for typical and escaped names.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to bcb11

This change adds label iteration and boundary helpers for decoded DNS names, with coverage for escaped, root, and ordinary names. No actionable merge-blocking risk remains after normal checks and review.

Poem

A rabbit hops through labels bright
Escaped dots stay in sight
NextLabel marks where names end
Tests compare each parsing friend
Benchmarks race through root and hare
Clean DNS paths now fill the air

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely identifies the two main additions: NextLabel and Question.Labels.
Docstring Coverage	✅ Passed	Docstring coverage is 88.89% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (1 skipped: 1 u…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 88.89% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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