Rename `option()` → `defineOption()` and `createPlugin()` → `definePlugin()`

[aryasaatvik]

Summary

The public API naming is inconsistent: defineCommand, defineConfig, defineGroup follow the define* pattern, but option() and createPlugin() do not. Rename all user-facing declarative APIs to use define* consistently.

Changes

Old	New
option()	defineOption()
createPlugin()	definePlugin()
createTestPlugin()	defineTestPlugin()

Hard break — no deprecation aliases. Bunli is pre-1.0.

Files to modify

Definitions:

• packages/core/src/types.ts — rename option() to defineOption()
• packages/core/src/plugin/create.ts — rename createPlugin() to definePlugin(), createTestPlugin() to defineTestPlugin()
• packages/core/src/plugin/index.ts — update re-exports
• packages/core/src/index.ts — update exports

Consumers (~60+ files):

• packages/cli/src/commands/ (8 files)
• packages/plugin-*/src/ (all plugin packages)
• packages/test/test/ and packages/core/test/
• examples/ (12 files across 3 example projects)
• packages/create-bunli/templates/ (6 template files)
• apps/web/ (hardcoded source strings in constants/monaco-setup)

Special care:

• packages/plugin-mcp/src/codegen.ts generates code that emits import { option } — must emit defineOption
• apps/web/src/api/workbench/constants.ts and apps/web/src/lib/monaco-setup.ts contain hardcoded template strings

Implementation notes

• Purely mechanical rename — no behavior changes
• Do this first to reduce noise in subsequent diffs
• Run bun build + bun test to verify no missed references
• Update CLAUDE.md code map references