fix(telemetry): review fixes — flush/shutdown ordering, session retirement, whole-exporter passthrough

Three review findings, each pinned by a red test first:

- The OTel backend retains the latest turn-boundary flush promise and
  shutdown() awaits it before provider.shutdown(): the SDK's
  concurrent-flush guard makes the shutdown-internal flush return early
  while one is in flight, silently dropping everything enqueued after
  the flush snapshot (including the coordinator's dispose-time shutdown
  markers).
- The coordinator retires sessions from the adopted set on
  session/disposed (mirroring the persistence coordinator): a long-lived
  backend no longer retains closed sessions and their event logs, and
  final unload no longer stamps shutdown markers for dead sessions.
- The exporter config passes through whole to OTLPLogExporter and its
  type/JSDoc now advertise the full OTLPExporterNodeConfigBase shape:
  rebuilding url/headers only silently dropped documented SDK options
  (timeoutMillis, compression, keepAlive, ...).

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

@@ -35,13 +35,20 @@ const handoffCursor = new WeakMap<Session, number>()
  * Registers the persistence-coordinator listener set plus the `agent/error`
  * relay, all through `ctx.effect()`/`ctx.on()` on the composing fiber, and
  * sweeps already-live sessions (a hot reload does not replay
- * `session/created`). Disposal emits each adopted session's `shutdown`
+ * `session/created`). A `session/disposed` retires the session from the
+ * adopted set — a long-lived backend must not retain closed sessions (and
+ * their frozen event logs) or stamp dispose-time markers for sessions that
+ * already ended. Disposal emits each still-adopted session's `shutdown`
  * operational record and then awaits the backend's `shutdown()`; a failure
  * there warns instead of throwing — best-effort reporting must not fail
  * application teardown.
  */
 export class TelemetryCoordinator {
-  /** Sessions adopted by THIS fiber, for dispose-time `shutdown` records and double-adoption protection. */
+  /**
+   * Sessions adopted by THIS fiber and still live, for dispose-time
+   * `shutdown` records and double-adoption protection; `session/disposed`
+   * retires entries.
+   */
   private readonly adopted = new Set<Session>()
   /** Per session, the `turn:step` keys whose first chunk already shipped; rebuilt from the log on re-adoption. */
   private readonly chunkSeen = new WeakMap<Session, Set<string>>()
@@ -57,6 +64,11 @@ export class TelemetryCoordinator {
     ctx.on('session/created', (session) => {
       this.adopt(session)
     })
+    // Retirement is observe-only: the projection/cursor WeakMaps die with the
+    // Session object; only the strong adopted set needs the explicit release.
+    ctx.on('session/disposed', (session) => {
+      this.adopted.delete(session)
+    })
     ctx.on('session/event', (session, event) => {
       this.contain(() => {
         this.capture(session, event)

packages/telemetry/session-telemetry/src/index.ts

@@ -108,9 +108,13 @@ export interface TelemetryBackend {
   flush?(): void
   /**
    * Forward the fiber's disposal to the SDK: flush whatever is queued and
-   * reach quiescence, per the SDK's own shutdown contract. Awaited by the
-   * coordinator's dispose; a rejection is logged as a warning and never
-   * fails application teardown.
+   * reach quiescence, per the SDK's own shutdown contract. Everything
+   * emitted before this call must still be delivered — including records
+   * enqueued while a {@link flush} hint is in flight, so a backend whose SDK
+   * guards against concurrent flushes orders behind the outstanding one (the
+   * coordinator emits its dispose-time `shutdown` markers immediately before
+   * calling this). Awaited by the coordinator's dispose; a rejection is
+   * logged as a warning and never fails application teardown.
    * @returns resolves when the backend's pipeline has quiesced.
    */
   shutdown(): Promise<void>