feat(opencode): Phase 1 - Backend data structure expansion for OpenCode support

Add OpenCode as the 4th supported application with additive provider management:

- Add OpenCode variant to AppType enum with all related match statements
- Add enabled_opencode field to McpApps and SkillApps structures
- Add opencode field to McpRoot and PromptRoot
- Add database schema migration v3→v4 with enabled_opencode columns
- Add settings.rs support for opencode_config_dir and current_provider_opencode
- Create opencode_config.rs module for config file I/O operations
- Update all services (proxy, mcp, skill, provider, stream_check) for OpenCode
- Add OpenCode support to deeplink provider and MCP parsing
- Update commands/config.rs for OpenCode config status and paths

Key design decisions:
- OpenCode uses additive mode (no is_current needed, no proxy support)
- Config path: ~/.config/opencode/opencode.json
- MCP format: stdio→local, sse/http→remote conversion planned
- Stream check returns error (not yet implemented for OpenCode)

src-tauri/src/services/provider/live.rs

@@ -120,6 +120,11 @@ pub(crate) fn write_live_snapshot(app_type: &AppType, provider: &Provider) -> Re
             // Delegate to write_gemini_live which handles env file writing correctly
             write_gemini_live(provider)?;
         }
+        AppType::OpenCode => {
+            // OpenCode uses additive mode - providers are written directly to config
+            // This will be fully implemented in Phase 3
+            log::debug!("OpenCode live snapshot not needed (additive mode)");
+        }
     }
     Ok(())
 }
@@ -220,6 +225,21 @@ pub fn read_live_settings(app_type: AppType) -> Result<Value, AppError> {
                 "config": config_obj
             }))
         }
+        AppType::OpenCode => {
+            use crate::opencode_config::{get_opencode_config_path, read_opencode_config};
+
+            let config_path = get_opencode_config_path();
+            if !config_path.exists() {
+                return Err(AppError::localized(
+                    "opencode.config.missing",
+                    "OpenCode 配置文件不存在",
+                    "OpenCode configuration file not found",
+                ));
+            }
+
+            let config = read_opencode_config()?;
+            Ok(config)
+        }
     }
 }
 
@@ -295,6 +315,24 @@ pub fn import_default_config(state: &AppState, app_type: AppType) -> Result<bool
                 "config": config_obj
             })
         }
+        AppType::OpenCode => {
+            // OpenCode uses additive mode - import from live is not the same pattern
+            // For now, return an empty config structure
+            use crate::opencode_config::{get_opencode_config_path, read_opencode_config};
+
+            let config_path = get_opencode_config_path();
+            if !config_path.exists() {
+                return Err(AppError::localized(
+                    "opencode.live.missing",
+                    "OpenCode 配置文件不存在",
+                    "OpenCode configuration file is missing",
+                ));
+            }
+
+            // For OpenCode, we return the full config - but note that OpenCode
+            // uses additive mode, so importing defaults works differently
+            read_opencode_config()?
+        }
     };
 
     let mut provider = Provider::with_id(