feat(babysitting): make unstable-agent-babysitter always-on by default

Remove the 'enabled' flag from babysitting config - the hook now runs
automatically when not disabled via disabled_hooks. This simplifies
configuration and makes the unstable model monitoring a default behavior.

BREAKING CHANGE: babysitting.enabled config option is removed. Use
disabled_hooks: ['unstable-agent-babysitter'] to disable the hook instead.

src/hooks/unstable-agent-babysitter/index.test.ts

@@ -76,7 +76,7 @@ describe("unstable-agent-babysitter hook", () => {
     const backgroundManager = createBackgroundManager([createTask()])
     const hook = createUnstableAgentBabysitterHook(ctx, {
       backgroundManager,
-      config: { enabled: true, timeout_ms: 120000 },
+      config: { timeout_ms: 120000 },
     })
 
     // #when
@@ -111,7 +111,7 @@ describe("unstable-agent-babysitter hook", () => {
     ])
     const hook = createUnstableAgentBabysitterHook(ctx, {
       backgroundManager,
-      config: { enabled: true, timeout_ms: 120000 },
+      config: { timeout_ms: 120000 },
     })
 
     // #when
@@ -139,7 +139,7 @@ describe("unstable-agent-babysitter hook", () => {
     ])
     const hook = createUnstableAgentBabysitterHook(ctx, {
       backgroundManager,
-      config: { enabled: true, timeout_ms: 120000 },
+      config: { timeout_ms: 120000 },
     })
 
     // #when
@@ -160,7 +160,7 @@ describe("unstable-agent-babysitter hook", () => {
     const backgroundManager = createBackgroundManager([createTask()])
     const hook = createUnstableAgentBabysitterHook(ctx, {
       backgroundManager,
-      config: { enabled: true, timeout_ms: 120000 },
+      config: { timeout_ms: 120000 },
     })
     const now = Date.now()
     const originalNow = Date.now