feat: add Hermes Agent as 6th supported app type (Phase 1)

Register AppType::Hermes across the entire Rust backend:
- Add Hermes variant to AppType enum with additive mode and MCP support
- Add hermes field to McpApps, SkillApps, CommonConfigSnippets, and all
  per-app structs (McpRoot, PromptRoot, VisibleApps, AppSettings)
- Create minimal hermes_config.rs with get_hermes_dir() respecting
  settings override, matching the pattern of other app config modules
- Update all match arms in commands, services, deeplink, proxy, mcp,
  session_manager, and test files
- Extract shared build_additive_app_settings() to eliminate duplication
  between OpenClaw and Hermes deep link handling
- Combine identical OpenClaw/Hermes proxy match arms into unified arms

src-tauri/src/proxy/providers/mod.rs

@@ -174,13 +174,9 @@ impl ProviderType {
                 }
                 ProviderType::Gemini
             }
-            AppType::OpenCode => {
-                // OpenCode doesn't support proxy, but return a default type for completeness
-                ProviderType::Codex // Fallback to Codex-like type
-            }
-            AppType::OpenClaw => {
-                // OpenClaw doesn't support proxy, but return a default type for completeness
-                ProviderType::Codex // Fallback to Codex-like type
+            AppType::OpenCode | AppType::OpenClaw | AppType::Hermes => {
+                // These apps don't support proxy, fallback to Codex-like type
+                ProviderType::Codex
             }
         }
     }
@@ -232,12 +228,8 @@ pub fn get_adapter(app_type: &AppType) -> Box<dyn ProviderAdapter> {
         AppType::Claude => Box::new(ClaudeAdapter::new()),
         AppType::Codex => Box::new(CodexAdapter::new()),
         AppType::Gemini => Box::new(GeminiAdapter::new()),
-        AppType::OpenCode => {
-            // OpenCode doesn't support proxy, fallback to Codex adapter
-            Box::new(CodexAdapter::new())
-        }
-        AppType::OpenClaw => {
-            // OpenClaw doesn't support proxy, fallback to Codex adapter
+        AppType::OpenCode | AppType::OpenClaw | AppType::Hermes => {
+            // These apps don't support proxy, fallback to Codex adapter
             Box::new(CodexAdapter::new())
         }
     }