feat: Extend AgentInfo with exitCode + add getAgentInputFiles/getAgentPrompt tRPC procedures

Adds exitCode to AgentInfo type and propagates it through all toAgentInfo()
implementations. Enhances getAgent to also return taskName and initiativeName
from their respective repositories. Adds two new filesystem-reading tRPC
procedures for the Agent Details tab: getAgentInputFiles (reads .cw/input/
files with binary detection, 500 KB cap, sorted) and getAgentPrompt (reads
.cw/agent-logs/<name>/PROMPT.md with 1 MB cap and structured ENOENT handling).

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

apps/server/agent/lifecycle/cleanup-strategy.ts

@@ -18,6 +18,7 @@ export interface AgentInfo {
   status: string;
   initiativeId?: string | null;
   worktreeId: string;
+  exitCode?: number | null;
 }
 
 export interface CleanupStrategy {

apps/server/agent/lifecycle/controller.ts

@@ -353,6 +353,7 @@ export class AgentLifecycleController {
       status: agent.status,
       initiativeId: agent.initiativeId,
       worktreeId: agent.worktreeId,
+      exitCode: agent.exitCode ?? null,
     };
   }
 }