feat: ACP base provider, Copilot integration, eliminate hardcoded provider unions (#170)

* feat(server): add ACP base provider with Claude ACP integration

Implement a generic Agent Client Protocol (ACP) base provider that any
ACP-compatible agent can extend with minimal code. Includes a concrete
Claude ACP implementation via @agentclientprotocol/claude-agent-acp
with full parity to the existing Claude Code provider.

The base handles subprocess lifecycle, streaming translation, permission
bridging, terminal/fs callbacks, listModels, loadSession/resume, and
mode/model management. The concrete class only specifies the command,
modes, and availability check.

* fix: update lockfile signatures and Nix hash

* feat: add Copilot ACP provider, eliminate hardcoded provider unions, fix ACP streaming bugs

Add Copilot as an ACP provider (copilot --acp), with real modes and models
discovered from the ACP server. Fix two ACP base bugs: duplicate assistant
text (emit deltas not cumulative) and idle→running→stuck (fire-and-return
startTurn). Replace all hardcoded provider string unions with string/manifest-
derived values so adding a provider only requires: impl class, manifest entry,
registry factory, icon, and E2E config. Add provider docs and Copilot icon.

* fix: update lockfile signatures and Nix hash

* feat(app): add OpenCode provider icon

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

packages/app/src/panels/agent-panel.tsx

@@ -11,9 +11,8 @@ import { AgentInputArea } from "@/components/agent-input-area";
 import { ArchivedAgentCallout } from "@/components/archived-agent-callout";
 import { FileDropZone } from "@/components/file-drop-zone";
 import type { ImageAttachment } from "@/components/message-input";
+import { getProviderIcon } from "@/components/provider-icons";
 import { ToastViewport, useToastHost } from "@/components/toast-host";
-import { ClaudeIcon } from "@/components/icons/claude-icon";
-import { CodexIcon } from "@/components/icons/codex-icon";
 import { useAgentAttentionClear } from "@/hooks/use-agent-attention-clear";
 import { useAgentInitialization } from "@/hooks/use-agent-initialization";
 import {
@@ -51,16 +50,14 @@ import {
 } from "@/screens/agent/agent-ready-screen-bottom-anchor";
 
 function formatProviderLabel(provider: Agent["provider"]): string {
-  if (provider === "claude") {
-    return "Claude";
-  }
-  if (provider === "codex") {
-    return "Codex";
-  }
   if (!provider) {
     return "Agent";
   }
-  return provider.charAt(0).toUpperCase() + provider.slice(1);
+  return provider
+    .split(/[-_\s]+/)
+    .filter((part) => part.length > 0)
+    .map((part) => part.charAt(0).toUpperCase() + part.slice(1))
+    .join(" ");
 }
 
 function resolveWorkspaceAgentTabLabel(title: string | null | undefined): string | null {
@@ -96,7 +93,7 @@ function useAgentPanelDescriptor(
   );
   const provider = descriptorState.provider;
   const label = resolveWorkspaceAgentTabLabel(descriptorState.title);
-  const icon = provider === "claude" ? ClaudeIcon : provider === "codex" ? CodexIcon : Bot;
+  const icon = getProviderIcon(provider) ?? Bot;
 
   return {
     label: label ?? "",