fix: migrate to TypeScript 6 — nodenext resolution + subpath imports

[Copilot]

TypeScript 6 deprecates moduleResolution: "node" (errors on build) and requires an explicit rootDir. This PR fixes all TS6 breaking changes and adopts modern Node.js subpath imports (#/).

tsconfig.json

• module + moduleResolution: "commonjs" / "node" → "nodenext" — correct semantic choice for a Node.js library; keeps CJS output (no "type": "module")
• Added rootDir: "src" (now required by TS6)
• lib: simplified to ["es2020", "dom"]; added explicit types: ["node"]
• Removed unused experimentalDecorators / emitDecoratorMetadata

Explicit .js extensions on all imports

nodenext resolution requires explicit extensions on relative imports (mirrors what Node.js needs at runtime). Updated all src/ and test/ files. jest.config.js gains a moduleNameMapper to strip .js so ts-jest resolves .ts source files:

moduleNameMapper: {
  '^(\\.{1,2}/.*)\\.js$': '$1',
  '^#/(.*)\\.js$': '<rootDir>/src/$1',
}

#/ subpath imports in src/

All intra-package imports now use Node.js subpath imports instead of relative paths:

// before
import { DataError } from '../../lib/Errors.js'

// after
import { DataError } from '#/lib/Errors.js'

package.json imports field wires the resolution:

"imports": {
  "#/*": {
    "types": "./src/*",
    "default": "./dist/*"
  }
}

• types condition → src/ (TypeScript resolves .js → .ts during compilation)
• default condition → dist/ (Node.js runtime on published package)

[Copilot]

Pull request overview

Migrates the project to TypeScript 6 by switching to nodenext module/moduleResolution, adding rootDir, and updating code/tests to use explicit .js extensions and internal #/ subpath imports.

Changes:

• Update tsconfig.json for TS6 (module/moduleResolution: nodenext, add rootDir, simplify lib, set types: ["node"]).
• Convert internal source imports to #/.../*.js and update tests to import ../src/.../*.js.
• Add package.json#imports and jest.config.js#moduleNameMapper to support #/ and .js-suffixed specifiers in TS/Jest.

Reviewed changes

Copilot reviewed 25 out of 27 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsconfig.json	Switch compiler to nodenext, set rootDir, adjust libs/types for TS6.
package.json	Add imports map for #/ self-references.
jest.config.js	Add moduleNameMapper to resolve .js-suffixed specifiers + #/ to src/ in tests.
src/JsonDB.ts	Replace relative imports with #/ imports and add .js extensions; update re-exports accordingly.
src/lib/JsonDBConfig.ts	Update adapter/lib imports to #/.../*.js.
src/lib/DBParentData.ts	Update imports to #/.../*.js.
src/lib/ArrayInfo.ts	Update imports to #/.../*.js.
src/lock/ReadWriteLock.ts	Update imports to #/.../*.js.
src/lock/Lock.ts	Update imports to #/.../*.js.
src/lock/Error.ts	Update imports to #/.../*.js.
src/adapter/data/JsonAdapter.ts	Update imports to #/.../*.js.
src/adapter/data/Serializers.ts	Update imports to #/.../*.js.
src/adapter/file/FileAdapter.ts	Update imports to #/.../*.js.
src/adapter/file/CipheredFileAdapter.ts	Update imports to #/.../*.js.
test/01-utils.test.ts	Add .js extensions to project-local imports.
test/02-jsondb.test.ts	Add .js extensions to project-local imports.
test/03-existing-db.test.ts	Add .js extensions to project-local imports.
test/04-array-utils.test.ts	Add .js extensions to project-local imports.
test/06-concurrency.test.ts	Add .js extensions to project-local imports.
test/07-cyphered.test.ts	Add .js extensions to project-local imports.
test/JsonDB.test.ts	Add .js extensions to project-local imports.
test/DBParentData.test.ts	Update mock/import paths to match new resolution approach.
test/ArrayInfo.test.ts	Add .js extensions to project-local imports.
test/adapter/Serializers.test.ts	Add .js extensions to project-local imports.
test/adapter/adapters.test.ts	Add .js extensions to project-local imports (and one local require).
test/lock/locks.test.ts	Add .js extensions to project-local imports.
test/lock/performance.test.ts	Add .js extensions to project-local imports.

[Copilot]

package.json sets imports["#/*"].types to ./src/*, but src/ is not included in the published files list (only dist/, README, LICENSE, CHANGELOG). That will break TypeScript resolution of the package’s internal #/... specifiers for consumers because the .d.ts files in dist/ will reference #/... and TS will follow the types condition to a path that isn’t shipped. Fix by either publishing src/ (add it to files) or by pointing the types condition at ./dist/* and using a separate dev-only mapping (e.g. tsconfig.paths) for building from src/.

Suggested change

	"types": "./src/*",
	"types": "./dist/*",