feat: expand magic prompts coverage and split generation prompts (#835)

- Add configurable visible/instructions prompt families for commit/PR generation, PR checks/comments flows, and git conflict resolution helpers.
- Refactor prompt sending to explicit visible + synthetic parts instead of newline-based splitting, with legacy override migration for old keys.
- Polish Magic Prompts settings UX with grouped sidebar entries, tooltip-based descriptions, AI icon, and validation that visible prompts cannot be empty across web and VS Code runtimes.

packages/web/server/lib/opencode/core-routes.js

@@ -161,6 +161,7 @@ export const registerCommonRequestMiddleware = (app, dependencies) => {
       req.path.startsWith('/api/projects') ||
       req.path.startsWith('/api/fs') ||
       req.path.startsWith('/api/git') ||
+      req.path.startsWith('/api/magic-prompts') ||
       req.path.startsWith('/api/prompts') ||
       req.path.startsWith('/api/terminal') ||
       req.path.startsWith('/api/opencode') ||