fix(e2b): address review round on cadence config, disposal, and SDK edge cases

- subprocess-e2b: the 20 ms remote poll cadence becomes a validated pollMs
  Config field (each tick is one control-plane request); the README documents
  the latency-versus-request-count trade.
- subprocess-e2b: extract src/remote.ts owning asError, signalOpts,
  commandOpts, delay, waitTick, and one tolerant signalRemoteGroups shared by
  the pgid-keyed process ladder and sid-keyed terminal ladder, so the two
  teardown paths keep identical error tolerance.
- subprocess-e2b: service disposal aggregates sibling cleanup failures into
  one AggregateError instead of discarding all but the first.
- subprocess-e2b: waitForProcessGroupId refuses published group ids <= 1, so
  a same-UID rewrite of the pid file cannot aim termination at kill -- -1;
  README documents the same-UID control-state limitation.
- subprocess-e2b: drain-grace expiry now releases an inherited-output E2B
  callback blocked on host backpressure before disconnecting, so the SDK
  settlement cannot stay pinned behind an unread host stream.
- subprocess-e2b: spawn/spawnTerminal stop validating typed spec fields
  (trust-TypeScript rule; pty-local validates its config before specs exist);
  resolveExecutable rejects separator-containing relative paths per the seam
  contract; terminal setups tracked as a Set of records.
- subprocess-e2b: PTY output push-without-backpressure is a documented
  contract (flowing consumer folds bytes; paused consumer buffers).
- fs-e2b: streamText normalizes the pinned SDK's empty-file '' return into an
  empty stream instead of throwing on getReader().
- e2b overlays: comment the one-world cwd invariant across e2b.cwd,
  workspaceRoot, and bash-local's implicit default workdir.

docs/config-catalog.md

@@ -1813,6 +1813,20 @@ export interface Config {
 
 Source: [`packages/subagent/subagent-spawn/src/index.ts:25`](../packages/subagent/subagent-spawn/src/index.ts)
 
+## `@deepseek-ai/dsh-subprocess-e2b`
+
+Requires: `e2b`
+
+```ts config-catalog
+/** Configuration for the E2B subprocess adapter. */
+export interface Config {
+  /** Remote status/liveness poll cadence in milliseconds; each tick is one control-plane request. */
+  pollMs?: number
+}
+```
+
+Source: [`packages/e2b/subprocess-e2b/src/index.ts:24`](../packages/e2b/subprocess-e2b/src/index.ts)
+
 ## `@deepseek-ai/dsh-system-prompt`
 
 ```ts config-catalog