Test SARIF Artefact wire format through public builders #399

Summary

Add behavioural tests through the public SARIF builders and JSON boundary for the renamed Rust API.

Rationale

The externally consumed SARIF contract requires physicalLocation.artifactLocation and artifacts. Existing tests primarily inspect Rust fields or round-trip values. Those tests do not prove that populated output uses canonical SARIF property names.

Affected areas

• crates/whitaker_sarif/src/builders/location_builder.rs
• crates/whitaker_sarif/src/builders/run_builder.rs
• crates/whitaker_sarif/src/model/location.rs
• crates/whitaker_sarif/src/model/run.rs
• Public SARIF integration or behavioural tests

Required changes

• Build a non-empty location and run through public builder APIs.
• Serialize the result at the JSON boundary.
• Assert that physicalLocation.artifactLocation and artifacts exist.
• Assert that artefactLocation and artefacts do not exist.
• Deserialize canonical SARIF JSON containing the canonical names and assert that Rust model values are populated.
• Add direct behavioural coverage for RunBuilder::with_artefact.

Acceptance criteria

• The test exercises public builders and serialized JSON.
• The test fails if the canonical property names change.
• The test verifies both serialization and deserialization of populated values.

Backlinks

• Pull request: Correct en-GB-oxendict spellings in code symbols and prose #363
• Requesting comment: Correct en-GB-oxendict spellings in code symbols and prose #363 (comment)
• Requested by: @leynos