CHE-16: fix runtime reconnect and late delivery consistency - #8

Summary

• give offline runtimes a bounded 60-second reconnect grace before failing active tasks
• treat a source-linked agent result comment as durable delivery evidence during late failure reconciliation
• keep the failed Run truthful while preventing duplicate retry and advancing a stranded in_progress issue to in_review
• exclude generated system failure comments and mismatched task lineage from delivery evidence

Verification

• PostgreSQL-backed reconnect and delivery consistency regression tests
• go test -race ./cmd/server ./internal/service -count=1
• go vet ./cmd/server ./internal/service ./pkg/db/generated

Related: CHE-16