Add monorepo export condition as alternative to source

[Copilot]

Packages can now use monorepo instead of source for internal monorepo references. This prevents publishing dev-only export conditions to npm while maintaining type-safety and tooling support within the monorepo.

Changes

Validation

• Requires publishConfig.exports when monorepo condition is present
• Enforces pnpm as package manager (via packageManager field or parent package.json)
• Made source field optional in PkgExport type to allow monorepo-only configs

Implementation

• Added package-manager-detector for package manager validation with monorepo support
• Made parseAndValidateExports async to enable package manager checks
• Created getSourcePath() utility to abstract source/monorepo field access
• Updated build, watch, and check tasks to handle both conditions

Example

{
  "packageManager": "pnpm@9.0.0",
  "exports": {
    ".": {
      "monorepo": "./src/index.ts",
      "default": "./dist/index.js"
    }
  },
  "publishConfig": {
    "exports": {
      ".": "./dist/index.js"
    }
  }
}

Existing packages using source continue to work unchanged.

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Latest commit: 9ce378e

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