chore: add coding conventions from nerve

- CLAUDE.md: functional-first, type over interface, no optional props, Result type
- biome.json: lint + format config (Biome 1.9)
- tsconfig.json: strict mode, composite project references
- .cursor/rules: global conventions + no-dynamic-import

Adapted from uncaged/nerve for bun workspace.

小橘 <xiaoju@shazhou.work>

.cursor/rules/global.mdc

@@ -0,0 +1,7 @@
+---
+description: Workflow project coding conventions — style, patterns, and toolchain
+globs: packages/*/src/**/*.ts
+alwaysApply: true
+---
+
+@CLAUDE.md