docs(rules): add tech stack to rules / roo code / ask mode

Author: adaptive-shield-matrix

.roo/rules-ask/tech.md

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+# Tech Stack
+
+- **Bun** - use `bun` instead of `npm` for all cli commands and package management
+- **Typescript** - Assume strict mode, add input/output types for all functions
+- **Solid.js**
+- **Vite** / **Rsbuild** - as build tools to generate a static website **SPA**
+- Hosted on **Cloudflare Pages**, deployed using the **Wrangler cli**
+- **Convex** - as backend for real time sync