fix(hooks): add missing trigger and channelId to agent_end, llm_input, and llm_output hook contexts

PR #28623 added trigger and channelId to PluginHookAgentContext and
threaded them through hookCtx for before_prompt_build, but missed the
separate context objects constructed for agent_end (line ~1974),
llm_input (line ~1766), and llm_output (line ~2034).

This caused ctx.trigger and ctx.channelId to always be undefined in
those hook handlers, breaking plugins that rely on trigger to
distinguish user-initiated vs memory/cron/heartbeat runs.

Aligns all hook context objects with hookCtx (line ~1636) so every
hook phase receives identical context fields.

🤖 AI-assisted

src/agents/pi-embedded-runner/run/attempt.ts

@@ -1774,6 +1774,8 @@ export async function runEmbeddedAttempt(
                   sessionId: params.sessionId,
                   workspaceDir: params.workspaceDir,
                   messageProvider: params.messageProvider ?? undefined,
+                  trigger: params.trigger,
+                  channelId: params.messageChannel ?? params.messageProvider ?? undefined,
                 },
               )
               .catch((err) => {
@@ -1982,6 +1984,8 @@ export async function runEmbeddedAttempt(
                 sessionId: params.sessionId,
                 workspaceDir: params.workspaceDir,
                 messageProvider: params.messageProvider ?? undefined,
+                trigger: params.trigger,
+                channelId: params.messageChannel ?? params.messageProvider ?? undefined,
               },
             )
             .catch((err) => {
@@ -2042,6 +2046,8 @@ export async function runEmbeddedAttempt(
               sessionId: params.sessionId,
               workspaceDir: params.workspaceDir,
               messageProvider: params.messageProvider ?? undefined,
+              trigger: params.trigger,
+              channelId: params.messageChannel ?? params.messageProvider ?? undefined,
             },
           )
           .catch((err) => {