refactor(agent): unify agent-scoped event signatures as payload objects

All agent/* and agent-loop/config-start-failed events take one payload
object carrying the agent subject; waterfall/serial payloads require a
signal and keep next as the final argument. PreStepContext and
RequestFailureContext are unfolded into payloads and retired.
goal/changed follows the same shape so agentEvents keeps its listener
error containment. ReactLoopAgent builds its scope carrier once in the
constructor. Regenerates scope resolvers, tool-cordis api catalog, and
docs catalogs; updates all affected listeners, tests, and the
core-data-structures docs (en + zh).

packages/session-persistence/session-checkpoint-policy/tests/session-checkpoint-policy.spec.ts

@@ -228,7 +228,7 @@ describe('session-checkpoint-policy tool and step boundaries', () => {
     ctx.on('session/flush', (current) => { flushed.push(current.id) })
     const signal = new AbortController().signal
     await agentEvents(ctx, agent).waterfall(
-      'agent/pre-step', [], { turn: 1, step: 1, signal },
+      'agent/pre-step', { messages: [], turn: 1, step: 1, signal },
       () => Promise.resolve({ kind: 'enter', messages: [] }),
     )
     expect(flushed).toEqual([session.id])