trim: drop unused waitForFirstDriveSync + supporting state

\`waitForFirstDriveSync\` had zero callers across the monorepo
(lib, react, svelte, e2e, data-browser, sveltekit-site,
integration tests). The supporting state
(\`_firstDriveSyncPromise\`, \`_firstDriveSyncResolve\`) was
also unused except by \`finishDriveSync\` resolving the latent
promise.

Also a latent flake risk: a caller awaiting this promise on a
session that never completes a drive sync (sustained offline,
or WS dying mid-handshake) would hang indefinitely — the
disconnect path didn't reject. Better that the API not exist
than ship that footgun.

Removed:
  - \`waitForFirstDriveSync()\` public method
  - \`_firstDriveSyncPromise\` + \`_firstDriveSyncResolve\` private state
  - The \`finishDriveSync\` resolve hook (now just clears state)

  pnpm typecheck clean, pnpm test 37/37.

Diff: −25 net.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: joepio

browser/lib/src/store.ts

@@ -1768,10 +1768,6 @@ export class Store {
     this._driveSyncInProgress = false;
     this._lastDriveSync = { drive, count, timestamp };
     this.emitSyncStatus();
-    if (this._firstDriveSyncResolve) {
-      this._firstDriveSyncResolve();
-      this._firstDriveSyncResolve = undefined;
-    }
   }
 
   /** True once any drive sync has finished in this session. Used by
@@ -1782,24 +1778,6 @@ export class Store {
     return this._lastDriveSync !== undefined;
   }
 
-  /** Resolves once the WebSocket has run its first drive-sync handshake
-   * (`SYNC_DIFF` + `SYNC_PUSH` complete, `finishDriveSync` called). Used by
-   * collection fetches to defer the fallback `/query` GET until the local
-   * WASM DB has been populated by the sync — the index then satisfies the
-   * query locally and the server round-trip can be skipped entirely.
-   * Resolves immediately if a sync has already completed in this session. */
-  public waitForFirstDriveSync(): Promise<void> {
-    if (this._lastDriveSync) return Promise.resolve();
-    if (!this._firstDriveSyncPromise) {
-      this._firstDriveSyncPromise = new Promise<void>(resolve => {
-        this._firstDriveSyncResolve = resolve;
-      });
-    }
-    return this._firstDriveSyncPromise;
-  }
-  private _firstDriveSyncPromise: Promise<void> | undefined;
-  private _firstDriveSyncResolve: (() => void) | undefined;
-
   public getSyncStatus(): StoreSyncStatus {
     return {
       serverConnected: this._serverConnected,