docs(audit): add M2 site-sync-pipeline implementation plan (#23)
8 bundles (A: race-fix + tiebreaker, B: SQLite writer + ring fallback,
C: gRPC proto + mapper, D: telemetry actor + ingest actor + gRPC handler,
E: host wiring, F: ESG audit emission via ScriptRuntimeContext wrapper,
G: SiteAuditWriteFailures health metric, H: component-level e2e test).
Brainstorm decisions locked: provenance via ScriptRuntimeContext wrapper,
push-primary telemetry, component-level e2e (no factory expansion),
mirror SiteEventLogger Channel<T> pattern for SqliteAuditWriter.