fix review findings: stale seam docs + race-free doneFor test helper

Codex review of the PR2 diff caught doc/comment sites doc-sync does not gate
(core-data-structures prose) and a latent test-helper race:
- docs/core-data-structures/persistence.md + bash.md, sqlite README, and two
  source comments (coordinator.ts, jsonl.spec.ts) still listed the removed
  has/delete/get/list methods — updated to the surviving four-method
  persistence surface and the get/list-free bash seam.
- doneFor(ctx, id) attached its onTaskDone listener lazily, after the task
  could already have closed (e.g. `true`), so it could miss the completion and
  hang. Replaced with trackCompletions(ctx): one eagerly-installed listener
  (mounted in setup() before any task starts) records every completion, and
  doneFor resolves immediately for an already-finished task or on completion
  otherwise. Race-free, and there is no get-by-id seam left to poll instead.

packages/session-persistence/session-persistence/src/coordinator.ts

@@ -202,7 +202,7 @@ export class PersistenceCoordinator<TornMarker = unknown> {
       throw new Error(`session "${meta.id}" already exists in this backend`)
     }
     // A persisted artifact under this id (in ANY scope) blocks creation: load/
-    // has/resume identify a session by id alone, so a second artifact would make
+    // resume identify a session by id alone, so a second artifact would make
     // resume nondeterministic.
     if (await this.backend.loadStored(meta.id) !== undefined) {
       throw new Error(`session "${meta.id}" already has a persisted log on disk; load/resume it instead of creating`)