feat(FN-3227): add startup model sync for opencode-go commands

- Add shared startup model sync helper and integrate it into dashboard, serve, and daemon command startup flows
- Introduce opencode-go model sync setting in core schema/types and expose it in dashboard settings UI
- Add CLI regression tests covering startup model sync behavior and command wiring
- Document the new startup model sync setting and related CLI behavior updates

Fusion-Task-Id: FN-3227

packages/core/src/settings-schema.ts

@@ -45,6 +45,7 @@ export const DEFAULT_GLOBAL_SETTINGS = {
   favoriteProviders: undefined,
   favoriteModels: undefined,
   openrouterModelSync: true,
+  opencodeGoModelSync: true,
   updateCheckEnabled: true,
   fnBinaryCheckEnabled: true,
   updateCheckFrequency: "daily",

packages/core/src/types.ts

@@ -1350,6 +1350,11 @@ export interface GlobalSettings {
    *  the OpenRouter API at startup so the model picker shows all available
    *  OpenRouter models (not just the static built-in list). Default: true. */
   openrouterModelSync?: boolean;
+  /** When true, startup refreshes the opencode-go model catalog via
+   *  `opencode models opencode --refresh` so model pickers expose an up-to-date
+   *  opencode-go provider list without waiting for a later session bootstrap.
+   *  Default: true. */
+  opencodeGoModelSync?: boolean;
   /** When true (default), checks npm for new versions of @runfusion/fusion and
    *  shows update notices in the CLI and dashboard. The actual cadence is
    *  governed by `updateCheckFrequency`. Disabled = no automatic checks at all. */