Close Task 10 renderer delivery gaps

Why:
- Independent review found trusted-boundary, semantic parity, replay-budget,
  comparison, persistence, cancellation, provenance, and routing gaps.
- Storage migration must include the new durable delivery table.

Evidence:
- go test -count=1 ./...
- go test -race ./internal/docgen ./internal/tools ./internal/runmgr
- go test ./... (deps/agent-document-renderer)
- go vet ./...
- go build ./...
- CGO_ENABLED=0 go build -trimpath ./cmd/agent-system
- Python house-style unittest suite and git diff --check

Impact:
- Word delivery now uses host-owned freezes, Markdown-first resumable persistence,
  closed registration boundaries, semantic shared rendering, and real comparison.
- Controlled/project documents still fail closed to RDM and non-Word flows remain
  unchanged.

Refs:
- Unified Document Renderer implementation plan Task 10
- /tmp/task10-backend-review-last.md
- Renderer d5cd8c126045a27d5a5cc5da23f64d3c737e116a

cmd/storage-migrate/main.go

@@ -286,6 +286,7 @@ func cmdBackup(args []string) error {
 var copyOrder = []string{
 	"projects", "users", "account_directory_revision", "profiles", "settings", "plugins",
 	"conversations", "runs", "messages", "project_work_outbox", "events", "artifacts",
+	"document_render_deliveries",
 	"hitl_cards", "human_decisions", "plans", "todos", "knowledge", "knowledge_vectors",
 	"activity_cards", "project_event_shares", "command_audit", "project_audit_links", "prompt_modules",
 	"sessions", "api_keys",