cdsr: wire the omp harness into the IDE as a native agent panel over ACP

Pin formulahendry.acp-client 0.2.0 (Open VSX, MIT, sha256-verified) and point
acp.agents at `omp acp`. OMP already ships an ACP v1 server, so no custom
extension and no marketplace exception were needed.

Verified in the running IDE: status bar `ACP: Oh My Pi`, session/list returns
real prior OMP sessions for the open folder, and a full prompt turn streams
text plus tool-call and plan cards.

Credentials never move: OMP authenticates from ~/.omp via its `agent` auth
method and the extension is given no key.

config/extensions.lock.json

@@ -97,6 +97,15 @@
       "reason": "Current Container Tools extension; its README states it replaces the older Docker extension functionality.",
       "mode": "baseline"
     },
+    {
+      "id": "formulahendry.acp-client",
+      "version": "0.2.0",
+      "platform": "universal",
+      "vsix_url": "https://open-vsx.org/api/formulahendry/acp-client/0.2.0/file/formulahendry.acp-client-0.2.0.vsix",
+      "sha256_url": "https://open-vsx.org/api/formulahendry/acp-client/0.2.0/file/formulahendry.acp-client-0.2.0.sha256",
+      "reason": "Generic Agent Client Protocol client. Drives the local omp harness via `omp acp` (ACP wire version 1), giving the IDE a native agent panel without a custom extension. MIT, engines.vscode ^1.85.0, no extensionKind so it loads in the remote extension host where child_process exists.",
+      "mode": "baseline"
+    },
     {
       "id": "sourcegraph.cody-ai",
       "version": "1.155.0",