[FIX] Update OpenCode and Copilot CLI handlers and paths

[xafr-odoo]

Description

Summary

This PR fixes execution, path resolution, and binary naming issues for both the opencode and copilot AI handlers, bringing them up to date with modern CLI package standards.

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Key Changes

1. OpenCode Handler (opencode)

• Binary Name Alignment: Changed binary target from opencode-cli to opencode so the handler works natively out-of-the-box with the current package without requiring manual symlinks.
• Dynamic Environment Resolution: Replaced hardcoded user NVM/Node paths with dynamic shutil.which lookups and a wildcard version directory scanner.
• Flag Updates: Replaced unsupported --add-dir flags with --auto for proper non-interactive execution.
• Type Safety: Ensured consistent string/Path object handling during .exists() checks.

2. Copilot Handler (copilot)

• Standalone CLI Support: Shifted execution away from the deprecated gh copilot extension wrapper in favor of the official standalone @github/copilot CLI package.
• Updated Guidance: Updated error logging/install hints to direct users to npm install -g @github/copilot.

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Safety & Backward Compatibility Check

• Fallback Preserved: The binary discovery order checks standard system $PATH first before inspecting local environment fallbacks (~/.local/bin, ~/.nvm/versions/node/*), keeping the handlers compatible with custom user installations.
• Non-Breaking Defaults: Standard flags like --resume, -m (model selection), and headless prompt switches remain unchanged, ensuring existing workflows continue operating smoothly.

Linked Issues

Link the issues that this PR solves, if any:

• Outdated suggested install for opencode & copilot #36

Compliance

• I have read the contribution guide
• I made sure the documentation is up-to-date both in doctrings and the docs directory
• I have added or modified unit tests where necessary
• I have added new libraries to the requirements.txt file, if any
• I have incremented the version number according the versioning guide
• The PR contains my changes only and no other external commit