feat: add ACP (Agent Client Protocol) server for editor integration

Adds full ACP support enabling hermes-agent to work as a coding agent
inside VS Code (via vscode-acp extension), Zed, JetBrains IDEs, and
any ACP-compatible editor.

## New module: acp_adapter/

- server.py: HermesACPAgent implementing all 15 Agent protocol methods
  (initialize, authenticate, new/load/list/fork/resume session, prompt,
  cancel, set mode/model/config, on_connect)
- session.py: Thread-safe SessionManager with per-session AIAgent lifecycle
- events.py: Callback factories translating hermes callbacks to ACP
  session_update notifications (tool_call, agent_thought, agent_message)
- tools.py: Tool kind mapping (20+ tools → read/edit/execute/search/fetch/think)
  and content builders (diffs for file edits, terminal output, text previews)
- permissions.py: Bridges hermes approval_callback to ACP requestPermission
  RPC for dangerous command approval dialogs in the editor
- auth.py: Provider credential verification
- entry.py: CLI entry point with .env loading and stderr logging

## Integration points

- run_agent.py: ACP tool bridge hook in _execute_tool_calls() for
  delegating file/terminal operations to the editor
- hermes_cli/main.py: 'hermes acp' subcommand
- pyproject.toml: [acp] optional dependency, hermes-acp entry point,
  included in [all] extras (auto-installed via install.sh)

## Supporting files

- acp_registry/agent.json: ACP Registry manifest
- acp_registry/icon.svg: Hermes caduceus icon
- docs/acp-setup.md: User-facing setup guide for VS Code, Zed, JetBrains

## Tests

- 41 new tests across 5 test files covering tools, sessions, permissions,
  server lifecycle, and auth
- Full test suite: 2901 passed, 0 failures

## User flow

1. hermes is already installed (install.sh)
2. Install 'ACP Client' extension in VS Code
3. Configure: command='hermes', args=['acp']
4. Chat with Hermes in the editor — diffs, terminals, approval
   dialogs, thinking blocks all rendered natively

acp_registry/agent.json

@@ -0,0 +1,12 @@
+{
+  "schema_version": 1,
+  "name": "hermes-agent",
+  "display_name": "Hermes Agent",
+  "description": "AI agent by Nous Research with 90+ tools, persistent memory, and multi-platform support",
+  "icon": "icon.svg",
+  "distribution": {
+    "type": "command",
+    "command": "hermes",
+    "args": ["acp"]
+  }
+}

acp_registry/icon.svg

@@ -0,0 +1,25 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" width="64" height="64">
+  <defs>
+    <linearGradient id="gold" x1="0%" y1="0%" x2="0%" y2="100%">
+      <stop offset="0%" style="stop-color:#F5C542;stop-opacity:1" />
+      <stop offset="100%" style="stop-color:#D4961C;stop-opacity:1" />
+    </linearGradient>
+  </defs>
+  <!-- Staff -->
+  <rect x="30" y="10" width="4" height="46" rx="2" fill="url(#gold)" />
+  <!-- Wings (left) -->
+  <path d="M30 18 C24 14, 14 14, 10 18 C14 16, 22 16, 28 20" fill="#F5C542" opacity="0.9" />
+  <path d="M30 22 C26 19, 18 19, 14 22 C18 20, 24 20, 28 24" fill="#D4961C" opacity="0.8" />
+  <!-- Wings (right) -->
+  <path d="M34 18 C40 14, 50 14, 54 18 C50 16, 42 16, 36 20" fill="#F5C542" opacity="0.9" />
+  <path d="M34 22 C38 19, 46 19, 50 22 C46 20, 40 20, 36 24" fill="#D4961C" opacity="0.8" />
+  <!-- Left serpent -->
+  <path d="M32 48 C22 44, 20 38, 26 34 C20 36, 18 42, 24 46 C18 40, 22 30, 30 28 C24 32, 22 38, 28 42"
+        fill="none" stroke="#F5C542" stroke-width="2.5" stroke-linecap="round" />
+  <!-- Right serpent -->
+  <path d="M32 48 C42 44, 44 38, 38 34 C44 36, 46 42, 40 46 C46 40, 42 30, 34 28 C40 32, 42 38, 36 42"
+        fill="none" stroke="#D4961C" stroke-width="2.5" stroke-linecap="round" />
+  <!-- Orb at top -->
+  <circle cx="32" cy="10" r="4" fill="#F5C542" />
+  <circle cx="32" cy="10" r="2" fill="#FFF8E1" opacity="0.7" />
+</svg>