Make PyREPL disabling conditional on Shell integration setting for Python 3.13+

[Copilot]

Problem

PyREPL (Python's enhanced REPL introduced in Python 3.13) causes cursor indentation issues when used with VS Code's Python shell integration feature. The previous implementation unconditionally disabled PyREPL for all Python 3.13+ environments by setting PYTHON_BASIC_REPL=1, but this prevented users from using PyREPL even when shell integration was disabled.

Solution

This PR makes PyREPL disabling conditional based on the user's shell integration preference:

• PyREPL is disabled (via PYTHON_BASIC_REPL=1) only when:
  • Python shell integration is enabled (python.terminal.shellIntegration.enabled = true) AND
  • Python version is 3.13 or higher
• PyREPL is allowed in all other cases

Behavior Matrix

Shell Integration	Python Version	PyREPL Status	Environment Variable
Disabled	Any	✅ Allowed	PYTHON_BASIC_REPL not set
Enabled	< 3.13	✅ Allowed	PYTHON_BASIC_REPL not set
Enabled	>= 3.13	❌ Disabled	PYTHON_BASIC_REPL=1
Enabled	Unknown	✅ Allowed	PYTHON_BASIC_REPL not set (safe fallback)

Changes Made

Core Implementation

• Modified registerBasicRepl() in src/client/terminals/pythonStartup.ts to conditionally set environment variable based on shell integration setting and Python version
• Added configuration change listener to dynamically update when shell integration setting is toggled
• Enhanced error handling for cases where Python version cannot be determined

Documentation

• Updated setting description in package.nls.json to inform users that PyREPL is automatically disabled when shell integration is enabled for Python 3.13+

Testing

• Added comprehensive test coverage for all conditional scenarios
• Tests verify correct behavior for different combinations of shell integration settings and Python versions

Benefits

1. Fixes cursor indentation issues: Resolves conflicts between PyREPL and shell integration
2. Preserves user choice: Users can still access PyREPL functionality when shell integration is disabled
3. Future-proof: Automatically applies to Python 3.14+ and later versions
4. Dynamic updates: Changes take effect immediately when settings are modified
5. Safe defaults: Graceful fallback when Python version detection fails

Fixes #25240.

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