feat(approval): the approval seam — one-shot permission decisions over a waterfall of answerers

ctx.approval (dsh-approval): request() dispatches the approval/request
waterfall and always resolves a closed outcome — allowed-once / rejected /
cancelled / unavailable — never rejects; zero listeners fall through to
fail-closed unavailable; abort settles cancelled and discards late answers;
throwing or rogue answerers are contained as unavailable; every ask lands
the log-only approval/asked / approval/decided audit pair. dsh-tools routes
a pre-execute ask through the seam opportunistically (ctx.get) with three
distinct deny reasons, keeping the historical ask→deny degrade when the
seam is absent.

The per-session policy tier, the ACP bridge answerer, and the sandbox
escalation asker are staged follow-ups of the approval-seam RFC.

packages/core/tools/package.json

@@ -23,6 +23,7 @@
   "license": "BSD-3-Clause",
   "peerDependencies": {
     "@deepseek-ai/dsh-agent": "^0.0.1",
+    "@deepseek-ai/dsh-approval": "^0.0.1",
     "@deepseek-ai/dsh-code-runtime": "^0.0.1",
     "@deepseek-ai/dsh-llm": "^0.0.1",
     "@deepseek-ai/dsh-session": "^0.0.1",
@@ -34,6 +35,7 @@
   },
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
+    "@deepseek-ai/dsh-approval": "workspace:^",
     "@deepseek-ai/dsh-code-runtime": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",