Skip coordinated seed downloads for a single owned network

Author: findolor

crates/common/ARCHITECTURE.md

@@ -146,17 +146,19 @@ Target gating is used extensively:
   the sync scheduler.
 - Browser startup starts all networks independently when any persisted target
   exists, retaining indexes and letting each missing network import its own
-  seed. A fresh DB coordinates missing targets under a shared Web Lock and their
-  per-network leadership locks. Ownership transfers directly to cold runners,
-  including on failure; networks led in another tab are left to their existing
-  runners. Seeds download in parallel; failed downloads leave only those targets
-  for retry, while successful downloads are rechecked against persisted
-  watermarks and imported together in one bounded sqlite-web session. A globally
-  fresh DB drops non-unique secondary indexes and rebuilds them once after all
-  seeds; additions to a populated DB retain existing indexes. A shared import
-  Web Lock covers watermark/index preflight through commit or cancellation for
-  both cohort and per-network imports; without that ownership, or after SDK
-  lease contention, imports retain indexes. PRIMARY KEY/UNIQUE indexes remain
+  seed. A fresh DB coordinates missing targets when it owns at least two
+  networks, under a shared Web Lock and their per-network leadership locks.
+  Ownership transfers directly to cold runners, including on failure; networks
+  led in another tab are left to their existing runners. Smaller cohorts use
+  their individual runners, retaining ownership and fresh-DB index deferral.
+  Seeds download in parallel; failed downloads leave only those targets for
+  retry, while successful downloads are rechecked against persisted watermarks
+  and imported together in one bounded sqlite-web session. A globally fresh DB
+  drops non-unique secondary indexes and rebuilds them once after all seeds;
+  additions to a populated DB retain existing indexes. A shared import Web Lock
+  covers watermark/index preflight through commit or cancellation for both
+  cohort and per-network imports; without that ownership, or after SDK lease
+  contention, imports retain indexes. PRIMARY KEY/UNIQUE indexes remain
   enforced. Cold network loops catch up, analyze their applied data and
   establish readiness; the cohort does not run an additional `ANALYZE`.
   Import/manifest failures and unsupported coordination fall back to per-network

crates/common/src/raindex_client/local_db/pipeline/runner/scheduler/wasm.rs

@@ -255,6 +255,11 @@ pub(crate) fn start(
                     }
                 }
             }
+            // A single runner already defers indexes on a fresh DB. Keep its
+            // ownership, but avoid cohort downloads and their timeout caps.
+            if cohort_settings.syncs.len() < 2 {
+                return Ok(());
+            }
             provision_missing_targets(
                 &db_clone,
                 &cohort_settings,