[TypeSpec Authoring] Integrate TypeSpec suppression tool into assessment

## Parent issue

Part of #14529.

## Goal

Integrate the TypeSpec team's suppression tool led by Catalina into the assessment evidence and decision flow.

## Scope

- Confirm the tool's supported inputs, outputs, versioning, availability, failure modes, and ownership with Catalina.
- Define an adapter that normalizes suppression results into the assessment result contract.
- Preserve raw suppression evidence, rationale, scope, and source locations for traceability.
- Surface valid suppressions and identify stale, invalid, or overly broad suppressions without silently hiding risk.
- Reconcile suppression results with assessment findings so suppressed findings remain distinguishable from resolved or absent findings.
- Define behavior when the tool is unavailable, fails, or returns incomplete evidence.

## Acceptance criteria

- Assessment can invoke a supported version of the tool and render normalized suppression status with source evidence.
- Suppressed findings remain visible with their rationale and scope.
- Stale, invalid, and unmatched suppressions are reported clearly.
- Tool failures produce a clear incomplete-analysis status rather than a safe result.
- Tests cover valid, stale, invalid, unmatched, malformed-output, and tool-failure cases.

Start by reviewing the assessment evidence and decision flow, then confirm the suppression tool’s supported inputs, outputs, versioning, availability, failure modes, and ownership with Catalina. Define the adapter boundary and traceability requirements before examining the requested test cases: valid, stale, invalid, unmatched, malformed-output, and tool-failure results. Done means normalized suppression status, visible rationale and scope, clear unmatched or stale results, and incomplete-analysis status on failure.

Written by the indexing model from the issue text.