refactor(tasks): drive wait() timing through dsh-timeout

ctx.tasks.wait arms a deadline() fusing the caller's abort with the
wait timeout and classifies the outcome with timeoutOf scoped to the
new TASK_WAIT_TIMEOUT code: a wait timeout resolves to the live
snapshot (the task keeps running), a caller abort rejects the wait —
same contract, no hand-rolled timer/listener plumbing, and a nested
foreign deadline can no longer misread as a wait timeout. task_output
deliberately declares NO ToolDefinition.timeoutMs: timeout-policy
turns a timed-out call into a structured TOOL_TIMEOUT failure, but a
timed-out wait is a SUCCESS that must still report [status: running]
(decision recorded in the runtime RFC alternatives).

pnpm-lock.yaml

@@ -893,6 +893,9 @@ importers:
       '@deepseek-ai/dsh-session':
         specifier: workspace:^
         version: link:../../core/session
+      '@deepseek-ai/dsh-timeout':
+        specifier: workspace:^
+        version: link:../../util/timeout
       cordis:
         specifier: ^4.0.0-rc.6
         version: 4.0.0-rc.6(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.4)