Bump Python minimum version to 3.9+

[Copilot]

The codebase uses PEP 585 generic type syntax (tuple[str, int]) which requires Python 3.9+. Python 3.8 raises TypeError: 'type' object is not subscriptable at runtime.

Changes

• python/pyproject.toml

  • requires-python: >=3.8 → >=3.9
  • Removed Python 3.8 from classifiers
  • Updated ruff target-version: py38 → py39

• python/README.md

  • Requirements section: Python 3.8+ → Python 3.9+

Users on Python 3.8 will now receive a clear installation error instead of runtime failures.

Original prompt

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This section details on the original issue you should resolve

<issue_title>client.py</issue_title>
<issue_description>*** Python 3.8.8 (default, Apr 13 2021, 15:08:07) [MSC v.1916 32 bit (Intel)] on win32. ***
On clien.py I cannot go beyond no matter what I tried
def _parse_cli_url(self, url: str) -> tuple[str,int]:

File "G:\python\copilot-sdk-main\python\copilot\client.py", line 138, in CopilotClient
def _parse_cli_url(self, url: str) -> tuple[str,int]:
TypeError: 'type' object is not subscriptable</issue_description>

<agent_instructions>Update pyproject.toml and python readmes to reflect that the minimum version is 3.9+</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes client.py #129

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[Copilot]

Pull request overview

This PR updates the documented and enforced minimum Python version for the Python SDK to 3.9+, aligning it with the use of PEP 585 generics that are not compatible with Python 3.8, so 3.8 users fail at install time instead of at runtime.

Changes:

• Raised requires-python in python/pyproject.toml from >=3.8 to >=3.9 and removed the Python 3.8 classifier.
• Updated Ruff configuration target-version from py38 to py39 to match the new minimum runtime version.
• Updated the Python SDK README requirements from “Python 3.8+” to “Python 3.9+” for consistency with packaging metadata.
  Note: Other repo docs still reference Python 3.8 (e.g., CONTRIBUTING.md, cookbook/python/recipe/README.md); consider updating those in a follow-up change.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/pyproject.toml	Bumps the minimum supported Python version to 3.9 in packaging metadata and linter configuration, removing Python 3.8 from classifiers.
python/README.md	Updates the documented Python version requirement from 3.8+ to 3.9+ for the Python SDK.

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