refactor: remove await using

[brunozoric]

Summary

• Replaced await using / AsyncDisposable on IReadStream with an explicit destroy() method
• Converted all call sites (NdJsonReaderTool.parseFile, tests) to try/finally
• Some bundlers choke on the explicit resource management syntax — this removes it without changing cleanup behavior

Changed files

• src/node/features/ReadStreamFactory/abstractions/ReadStreamFactory.ts — IReadStream no longer extends AsyncDisposable, adds destroy()
• src/node/features/ReadStreamFactory/ReadStreamFactory.ts — Symbol.asyncDispose → destroy()
• src/node/features/NdJsonReaderTool/NdJsonReaderTool.ts — await using → try/finally
• __tests__/node/ReadStreamFactory.test.ts — all tests updated to use try/finally + destroy()
• Docs: README.md, AGENTS.md, feature README.md updated

Test plan

• All 447 tests pass
• Typecheck clean
• Build clean
• No memory/resource leak — destroy() calls same stream.destroy() that AsyncDisposable did