feat: implement Radar backend tRPC procedures with repository extensions

Add five new tRPC query procedures powering the Radar page's per-agent
behavioral metrics (questions asked, subagent spawns, compaction events,
inter-agent messages) plus the batch repository methods they require.

Repository changes:
- LogChunkRepository: add findByAgentIds() for batch fetching without N+1
- ConversationRepository: add countByFromAgentIds() and findByFromAgentId()
- Drizzle adapters: implement all three new methods using inArray()
- InMemoryConversationRepository (integration test): implement new methods

tRPC procedures added:
- agent.listForRadar: filtered agent list with per-agent metrics computed
  from log chunks (questionsCount, subagentsCount, compactionsCount) and
  conversation counts (messagesCount); supports timeRange/status/mode/initiative filters
- agent.getCompactionEvents: compact system init chunks for one agent (cap 200)
- agent.getSubagentSpawns: Agent tool_use entries with prompt preview (cap 200)
- agent.getQuestionsAsked: AskUserQuestion tool calls with questions array (cap 200)
- conversation.getByFromAgent: conversations by fromAgentId with toAgentName resolved

All 13 new unit tests pass; existing test suite unaffected.

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

apps/server/test/integration/real-providers/conversation.test.ts

@@ -88,6 +88,24 @@ class InMemoryConversationRepository implements ConversationRepository {
     return updated;
   }
 
+  async countByFromAgentIds(agentIds: string[]): Promise<{ agentId: string; count: number }[]> {
+    if (agentIds.length === 0) return [];
+    const counts = new Map<string, number>();
+    for (const conv of this.store.values()) {
+      if (agentIds.includes(conv.fromAgentId)) {
+        counts.set(conv.fromAgentId, (counts.get(conv.fromAgentId) ?? 0) + 1);
+      }
+    }
+    return [...counts.entries()].map(([agentId, count]) => ({ agentId, count }));
+  }
+
+  async findByFromAgentId(agentId: string): Promise<Conversation[]> {
+    return [...this.store.values()]
+      .filter((c) => c.fromAgentId === agentId)
+      .sort((a, b) => a.createdAt.getTime() - b.createdAt.getTime())
+      .slice(0, 200);
+  }
+
   /** Test helper — return all conversations */
   getAll(): Conversation[] {
     return [...this.store.values()];