Issue 21840: isolated Linux dev server, real browser, seeded stopped threads.
Before: origin/main 8d3b061121.
Authenticated GET bounded snapshot: HTTP 200.
{
  "name": "sql.transaction",
  "durationMs": 13.297433,
  "attributes": {
    "db.name": "statev2.sqlite",
    "service.name": "t3code-server",
    "db.system.name": "sqlite",
    "db.connection": "writer",
    "db.lock_wait_ms": 0.03
  },
  "exit": {
    "_tag": "Success"
  }
}
Small fixture: does not measure reporter cold-cache 10GB latency.

After: b16843cb8db770b43717e3717afd8677ca11ac4a (tree identical to 247703a96b; preserves original contributor commit and current main).
Same browser and seeded state; explicit protocol header 2; authenticated bounded HTTP 200, browser duration 52.2ms.
{
  "name": "sql.transaction",
  "durationMs": 32.62845,
  "attributes": {
    "db.name": "statev2.sqlite",
    "service.name": "t3code-server",
    "db.system.name": "sqlite",
    "db.connection": "reader",
    "db.lock_wait_ms": 0.016
  },
  "exit": {
    "_tag": "Success"
  }
}

Red test at 9f597f2058: snapshot must return while another connection holds the writer; SqlError/LockTimeoutError database is locked.
Green at 247703a96b: 37/37 ProjectionStore + ThreadSearch and 16/16 nodeSqliteClient passed; scoped server typecheck, format and lint passed.
No render paths changed. No 10GB cold-cache timing claim.