added copilot-instructions.md file

Author: wasin-waeosri

.github/copilot-instructions.md

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+# Copilot Instructions for This Repository
+
+## Project scope
+
+This repository is a Python sample for consuming LSEG Machine Readable News over WebSocket connections.
+
+- `mrn_console_rtds.py` is the RTDS console example.
+- `mrn_console_rto_v2.py` is the RTO version 2 authentication console example.
+- `notebook/` contains notebook variants of the same workflows.
+
+## Working rules
+
+- Keep changes small and targeted. This repo is a sample application, not a framework.
+- Preserve the existing separation between RTDS and RTO flows unless the task explicitly requires combining them.
+- Prefer straightforward standard-library Python solutions unless the repository already depends on a package for the task.
+- Match the existing script style in the file you are editing. Do not reformat unrelated code.
+
+## Files to avoid editing
+
+- Do not modify files under `mrn_python/`. This directory is a checked-in virtual environment and vendored dependency tree.
+- Do not edit files under `mrn_python/Lib/site-packages/` to change application behavior.
+- Only update dependency files such as `requirements.txt` or `requirements_notebook.txt` when the task actually requires a new dependency or a version change.
+
+## Configuration and secrets
+
+- Never hardcode credentials, tokens, hostnames, or customer-specific identifiers.
+- For RTO version 2 configuration, follow the `.env` pattern shown in `.env.example`.
+- If configuration changes are needed, update `.env.example` and `README.md` together when appropriate.
+
+## Python and runtime expectations
+
+- Target Python 3.10 compatibility unless the task explicitly requires something else.
+- Keep console output compatible with the repository's current UTF-8 handling.
+- MRN payload handling depends on base64 decoding and gzip/zlib decompression. Preserve that behavior and be careful around fragment assembly logic.
+
+## Validation guidance
+
+- For changes in Python scripts, prefer narrow validation such as `python -m py_compile <file>`.
+- If documentation changes affect setup or execution, keep command examples consistent with `README.md`, `Dockerfile`, and the current entry scripts.
+
+## Documentation expectations
+
+- Keep README changes aligned with the actual file layout in this repo.
+- Use the existing terminology from the project: RTDS, RTO, MRN, fragment assembly, and WebSocket API.
+- When adding new instructions, prefer practical run steps over broad background material.