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/host/apiproxy/tests/api-proxy-fork.spec.ts

@@ -280,7 +280,7 @@ describe('sessions.fork', () => {
     })
     const fallback: LlmCallConfig = { provider: 'default-provider', model: 'default-model' }
     await expect(agentEvents(child.ctx, child).waterfall(
-      'agent/request', 1, 0, new AbortController().signal, () => Promise.resolve(fallback),
+      'agent/request', { turn: 1, step: 0, signal: new AbortController().signal }, () => Promise.resolve(fallback),
     )).resolves.toMatchObject({
       provider: 'inherited-provider',
       model: 'inherited-model',