Connection Foundation and Parser Refactoring

[tobiu]

Goal

Establish the Neo.data.connection.Base hierarchy and fix the abstraction leak in Neo.data.parser.Stream by extracting its network transport logic.

Context

A Parser should strictly focus on deserialization and shaping data (e.g., converting a text stream into JSON records). Currently, Neo.data.parser.Stream has fetch() and AbortController logic hardcoded into its read() method. This makes it a Connection in disguise and violates the single responsibility principle.

Acceptance Criteria

• Create src/data/connection/Base.mjs.
• Refactor Neo.data.connection.Fetch and Xhr to extend this new Base class.
• Create a new Connection (e.g., connection.Stream or enhance connection.Fetch) that handles the fetch() request and returns the ReadableStream.
• Refactor Neo.data.parser.Stream: Remove the fetch() call. The parser should now accept the ReadableStream provided by the Connection, process the NDJSON/JSONL chunks, and yield records.
• Ensure the Pipeline class correctly routes the output of the Connection into the Parser.