Improve search issue drafts and recipe workflows

[Widthdom]

Summary

• Add ad hoc search --format issue-drafts output with issue title/label hints.
• Add GitHub-backed duplicate preflight for issue drafts, including suggestions export --format issue-drafts parity.
• Expose recipe metadata/replay commands, child query selection, and compact recipe pagination.

Documentation and Changelog

• Updated USER_GUIDE.md for the new issue-draft and recipe workflow flags/output.
• Added changelog fragments:
  • changelog.d/unreleased/3520.added.md
  • changelog.d/unreleased/3449.added.md
  • changelog.d/unreleased/3447.added.md
  • changelog.d/unreleased/3519.added.md
  • changelog.d/unreleased/3392.added.md

Validation

• dotnet build
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~IssueDuplicatePreflightTests"
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~QueryCommandRunnerTests.RunSearch|FullyQualifiedName~ConsoleUiTests|FullyQualifiedName~IssueDuplicatePreflightTests|FullyQualifiedName~CliFlagSchemaTests|FullyQualifiedName~ProgramCliTests.Suggestions_ExportIssueDrafts"
• dotnet run --project tools/CodeIndex.Changelog -- check
• git diff --check origin/main..HEAD
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json

Adversarial Review

• Round 1 found two actionable Issue-draft duplicate preflight should fetch open GitHub issues directly #3449 issues: GitHub html_url should be preferred over REST url, and stale duplicate --open-issues <path> USER_GUIDE rows should be removed. Both were fixed.
• Round 2: No blocking/actionable issues found.

Follow-Up

• None.

Fixes #3520
Fixes #3449
Fixes #3447
Fixes #3519
Fixes #3392