Remove contextMode, consolidate wake policies, and default serveUi to true

Drop the unused contextMode field from the agent schema, shared types, validators,
and all UI references. Merge wakeOnOnDemand and wakeOnAutomation into a single
wakeOnDemand toggle. Default serveUi to true and remove the onboarding prompt for it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/agent-config-primitives.tsx

@@ -33,11 +33,8 @@ export const help: Record<string, string> = {
   intervalSec: "Seconds between automatic heartbeat invocations.",
   timeoutSec: "Maximum seconds a run can take before being terminated. 0 means no timeout.",
   graceSec: "Seconds to wait after sending interrupt before force-killing the process.",
-  wakeOnAssignment: "Automatically wake this agent when a new issue is assigned to it.",
-  wakeOnOnDemand: "Allow this agent to be woken on demand via the API or UI.",
-  wakeOnAutomation: "Allow automated systems to wake this agent.",
+  wakeOnDemand: "Allow this agent to be woken by assignments, API calls, UI actions, or automated systems.",
   cooldownSec: "Minimum seconds between consecutive heartbeat runs.",
-  contextMode: "How context is managed between runs (thin = fresh context each run).",
   budgetMonthlyCents: "Monthly spending limit in cents. 0 means no limit.",
 };