fix(web): review round 1 — loud opt-out, headless drain, scaffold isolation, docs

- resolveTelemetryPatch: extracted pure switch resolution (unit-tested);
  fails loud when DSH_TELEMETRY_DISABLED is set but the row is absent, and
  documents that ANY non-empty value (including '0'/'false') disables.
- runHeadless: SIGINT/SIGTERM now dispose the tree before exit so the
  telemetry tail and shutdown marker drain (Node's default signal exit
  skips disposal).
- web.cordis.yml: explicit maxQueueSize beside maxExportBatchSize (the
  single-batch drain invariant no longer leans on an SDK default), comment
  covers exportTimeoutMillis's role and links the Agent Note.
- apps/web scaffold: disable telemetry-otel — fixture sessions must never
  leave the process.
- apps/cli README (en/zh + pairing): document the default endpoint, both
  env seams, and the no-redaction disclosure.

apps/cli/src/headless.ts

@@ -82,6 +82,17 @@ export async function runHeadless(task: string): Promise<void> {
   })
   const { ctx, port } = await entry.run()
   const dispose = async (): Promise<void> => { await ctx.fiber.dispose() }
+  // Signal exits must still dispose the tree: the composition mounts
+  // exit-drained plugins (telemetry's queued tail and shutdown marker would
+  // otherwise be lost), and Node's default signal exit skips disposal.
+  let signalled = false
+  const disposeAndExit = (code: number): void => {
+    if (signalled) return
+    signalled = true
+    void dispose().finally(() => { process.exit(code) })
+  }
+  process.on('SIGTERM', () => { disposeAndExit(143) })
+  process.on('SIGINT', () => { disposeAndExit(130) })
   // The headless session is web-observable while it runs (same composition).
   process.stderr.write(`dsh: observing at http://127.0.0.1:${String(port)}\n`)
   const api = new InProcessApiClient(toFetchHandler(ctx.apiProxy))