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/deeplink/mcp.rs

@@ -166,6 +166,7 @@ pub(crate) fn parse_mcp_apps(apps_str: &str) -> Result<McpApps, AppError> {
         claude: false,
         codex: false,
         gemini: false,
+        opencode: false,
     };
 
     for app in apps_str.split(',') {
@@ -173,6 +174,7 @@ pub(crate) fn parse_mcp_apps(apps_str: &str) -> Result<McpApps, AppError> {
             "claude" => apps.claude = true,
             "codex" => apps.codex = true,
             "gemini" => apps.gemini = true,
+            "opencode" => apps.opencode = true,
             other => {
                 return Err(AppError::InvalidInput(format!(
                     "Invalid app in 'apps': {other}"

src-tauri/src/deeplink/provider.rs

@@ -145,6 +145,7 @@ pub(crate) fn build_provider_from_request(
         AppType::Claude => build_claude_settings(request),
         AppType::Codex => build_codex_settings(request),
         AppType::Gemini => build_gemini_settings(request),
+        AppType::OpenCode => build_opencode_settings(request),
     };
 
     // Build usage script configuration if provided
@@ -363,6 +364,33 @@ fn build_gemini_settings(request: &DeepLinkImportRequest) -> serde_json::Value {
     json!({ "env": env })
 }
 
+/// Build OpenCode settings configuration
+fn build_opencode_settings(request: &DeepLinkImportRequest) -> serde_json::Value {
+    let endpoint = get_primary_endpoint(request);
+
+    // Build options object
+    let mut options = serde_json::Map::new();
+    if !endpoint.is_empty() {
+        options.insert("baseURL".to_string(), json!(endpoint));
+    }
+    if let Some(api_key) = &request.api_key {
+        options.insert("apiKey".to_string(), json!(api_key));
+    }
+
+    // Build models object
+    let mut models = serde_json::Map::new();
+    if let Some(model) = &request.model {
+        models.insert(model.clone(), json!({ "name": model }));
+    }
+
+    // Default to openai-compatible npm package
+    json!({
+        "npm": "@ai-sdk/openai-compatible",
+        "options": options,
+        "models": models
+    })
+}
+
 // =============================================================================
 // Config Merge Logic
 // =============================================================================