feat(T-571): voeg SKIPPED toe aan ClaudeJobStatus enum

Reactie op PBI-33 batch waar worker correct detecteerde dat werk al
gemerged was, maar geen passende status had om dat uit te drukken.
SKIPPED is bedoeld voor jobs met verify=EMPTY/DIVERGENT waar de
diff t.o.v. origin/main leeg is — geen FAILED (geen fout), geen DONE
(geen netto-output).

Migratie: ALTER TYPE ClaudeJobStatus ADD VALUE 'SKIPPED'.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prisma/migrations/20260505230512_add_skipped_to_claude_job_status/migration.sql

@@ -0,0 +1,6 @@
+-- Add SKIPPED to ClaudeJobStatus enum.
+-- Used for jobs where the worker correctly detects that the work was already
+-- merged before the job ran (verify=EMPTY/DIVERGENT with no net diff).
+-- Distinct from FAILED (genuine errors) and DONE (new commit produced).
+
+ALTER TYPE "ClaudeJobStatus" ADD VALUE 'SKIPPED';

prisma/schema.prisma

@@ -37,6 +37,7 @@ enum ClaudeJobStatus {
   DONE
   FAILED
   CANCELLED
+  SKIPPED
 }
 
 enum VerifyResult {