feat(policies): add assessment annotation to policy finding schemas

Extends PolicyVulnerabilityFinding, PolicySASTFinding and
PolicyLicenseViolationFinding with an optional PolicyAssessmentResult
field carrying the precedence-resolved effective_status and the
matching individual assessments. The policy engine populates this via
the chainloop.effective_assessments builtin; it then round-trips
through ValidateFinding into the CAS-stored PolicyEvaluationBundle.

Schema-only change. Replaces #3093.

Assisted-by: Claude Code
Signed-off-by: Miguel Martinez Trivino <miguel@chainloop.dev>

Author: migmartri