feat(server): add DCP clean-room context pruning

- Deduplication: removes consecutive identical tool_call+tool_result pairs
- Purge-errors: removes failed/empty tool results
- Transform orchestrator runs strategies in sequence pre-payload
- Wired into turn.ts before buildMessagesPayload
- Clean-room reimplementation (AGPL reference: behavior only)

apps/server/src/services/inference/dcp/messages.ts

@@ -0,0 +1,34 @@
+// DCP message shape adapter.
+// Converts between BooCode MessagePart[] and the DCP internal shape.
+// Clean-room implementation — no AGPL source copied.
+
+export interface DcpMessage {
+  role: 'user' | 'assistant' | 'tool';
+  content: string;
+  tool_call_id?: string;
+  tool_calls?: Array<{ id: string; name: string; arguments: string }>;
+  isError?: boolean;
+}
+
+export function toDcpMessages(parts: any[]): DcpMessage[] {
+  return parts.map((p: any) => {
+    const msg: DcpMessage = { role: p.role, content: p.content ?? '' };
+    if (p.tool_call_id) msg.tool_call_id = p.tool_call_id;
+    if (p.tool_calls) msg.tool_calls = p.tool_calls;
+    if (p.isError) msg.isError = true;
+    if (p.role === 'tool' && p.content && p.content.startsWith('Error:')) {
+      msg.isError = true;
+    }
+    return msg;
+  });
+}
+
+export function fromDcpMessages(msgs: DcpMessage[]): any[] {
+  return msgs.map((m) => ({
+    role: m.role,
+    content: m.content,
+    ...(m.tool_call_id ? { tool_call_id: m.tool_call_id } : {}),
+    ...(m.tool_calls ? { tool_calls: m.tool_calls } : {}),
+    ...(m.isError ? { isError: true } : {}),
+  }));
+}