Expand test coverage and extract cloud support decision logic

[jasonjoh]

Summary

Expands the test suite from 12 to 90 tests and extracts the previously-untested cloud-support decision logic out of Program.cs into a testable unit.

Changes

Extracted decision logic

• New CloudSupportStatusEvaluator (src/Docs/) with:
  • Merge(accumulated, operationStatus, out mismatch) — combines an operation's status into the running total, OR-combining when known statuses disagree (surfacing a mismatch flag so callers still log the warning).
  • RequiresVersionPivot(v1Status, betaStatus) — decides whether a doc needs separate v1/beta include lines.
• Refactored all four call sites in Program.cs (root-command loop + v1/beta loops in the copilot command + the version-pivot if). Behavior and log output are preserved exactly.

New test coverage

• Cloud-matching engine — GetNodeByPath ({id} matching, () function suffix, unknown-path null) and GetCloudSupportStatus (Global / AllClouds / GlobalAndChina, method-not-present, null method, US Gov L5 exclusion stripping), backed by minimal OpenAPI YAML fixtures.
• OpenAPIOverrides — override remapping (operation constraints, case-insensitivity), per-path+method+cloud exclusion (incl. backslash normalization), and per-file exclusion.
• INCLUDE mapping/writers — all 8 CloudSupportStatus → include-file mappings, unmapped-status throw, update-in-place, and the zone-pivoted writer.
• ApiOperation — parsing plus error paths (empty, missing path, invalid HTTP method).
• StringExtensions — the 9 previously-untested methods, incl. IsEqualIgnoringCase's OData-parameter branch.
• DocSet — recursive loading and doc_type skipping (conceptual + missing doc_type).
• CloudSupportStatusEvaluator — full unit coverage of both methods.

Testing

dotnet test → 90 passed, 0 failed.

Tests touching the static OpenAPIOverrides state are serialized via a shared xUnit collection to avoid cross-class races; INCLUDE-writing tests operate on temp copies so committed fixtures are never modified.