fix(e2b): address the v7 review round

- restore the parent's AGENTS.md body around this branch's e2b row (the
  replay had resurrected the pre-profile-CLI layout, deleting the api/,
  bundle/, settings/, and credentials/ groups); the fs/lsp row
  condensations stay for the word budget
- aggregate the composite rollback failure, not the original error, when
  private state cleanup also fails — a surviving remote group is no
  longer hidden by a later cleanup error (triple-failure regression)
- own the state directory before the makeDir RPC, matching the terminal
  transaction, so a cancellation racing a committed creation still
  enters cleanup
- drop the hidden pollMs parameter defaults; the schemastery default is
  the one home, and tests pass the cadence explicitly
- restore spawn/spawnTerminal graceMs validation to the seam's
  documented bound (the earlier removal cited subprocess-local as not
  validating; it does), with rejection regressions

packages/e2b/subprocess-e2b/src/process.ts

@@ -194,7 +194,7 @@ export class E2BSubprocessHandle implements SubprocessHandle {
     private readonly runtime: E2BSandboxService,
     private readonly spec: SubprocessSpawnSpec,
     readonly stateDir: string,
-    private readonly pollMs = 20,
+    private readonly pollMs: number,
   ) {
     this.paths = {
       pid: posix.join(stateDir, 'pid'),
@@ -378,7 +378,7 @@ export class E2BSubprocessHandle implements SubprocessHandle {
           await this.removeFailedState(sandbox)
         } catch (cleanupError: unknown) {
           failure = new AggregateError(
-            [error, cleanupError],
+            [failure, cleanupError],
             'subprocess-e2b: command failed and private state cleanup failed',
           )
         }
@@ -398,8 +398,10 @@ export class E2BSubprocessHandle implements SubprocessHandle {
     const signal = this.terminationController.signal
     const ambient = await readRemoteEnvironment(sandbox, signal)
     this.controlEnvs = bootstrapEnvironment(ambient)
-    await sandbox.files.makeDir(this.stateDir, { signal })
+    // Own the directory before the request: a cancellation racing a committed
+    // creation must still enter cleanup (removal tolerates an absent path).
     this.stateDirectoryCreated = true
+    await sandbox.files.makeDir(this.stateDir, { signal })
     await sandbox.commands.run(
       `chmod 700 -- ${quoteE2BShellArg(this.stateDir)}`,
       commandOpts(this.controlEnvs, signal),