Harden catalog vendor resolution and agent prompt

Address review feedback on the agent-driven tracker catalog path:

- Return initiator-domain load failures instead of swallowing them,
  so the worker retries rather than running the agent on partial
  context.
- In the resolver, treat only ErrResourceNotFound as a catalog miss
  and propagate genuine name/slug lookup errors.
- Insert the new vendor inside a savepoint and, on the slug
  unique-violation race, reload and return the winning row instead of
  aborting the caller's transaction.
- Stop seeding common_third_party_domains from observed initiator
  domains. They are a co-occurrence signal, not verified ownership,
  and writing them into the global cross-tenant catalog pollutes the
  domain-based matcher. The curated seed owns that data.
- Warn the mapping agent that observed domains may belong to shared
  CDNs, tag managers, or hosting infrastructure rather than the
  vendor, so it does not attribute on that basis alone.
- Extract a shared tracker-identification prompt helper and move the
  common-pattern identification prompt next to the enrichment agent.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/cookiebanner/common_pattern_enrichment_agent.go

@@ -75,6 +75,15 @@ func buildCommonPatternEnrichmentAgent(
 	return agent.New("common-pattern-enrichment", cfg.LLMClient, opts...)
 }
 
+// buildCommonPatternIdentificationPrompt builds the mapping-agent input
+// for a global catalog pattern. Catalog rows carry no observed domains,
+// so the prompt omits the <observed_domains> signal and relies on the
+// pattern name, type, and naming conventions. It lets the enrichment
+// worker reuse the mapping agent to attribute a vendor before describing.
+func buildCommonPatternIdentificationPrompt(cp coredata.CommonTrackerPattern) string {
+	return buildTrackerIdentificationPrompt(cp.Pattern, cp.TrackerType, cp.MatchType, cp.MaxAgeSeconds)
+}
+
 func buildEnrichmentPrompt(cp coredata.CommonTrackerPattern, thirdPartyName string) string {
 	maxAge := "session"
 	if cp.MaxAgeSeconds != nil {