feat(core): improve logging for plugin auto-installation

[michaelbe812]

Summary

• Add user confirmation prompt before auto-installing packages (y/n)
• Log detected package manager (npm/pnpm/yarn) when installing
• Hide stack traces from user-facing logs, show full details in debug/verbose mode only
• Add skipPrompt option to loadPlugin() for programmatic usage

Closes #73

Changes

User-Facing Improvements

Before:

Loading plugin: openapi-tools
Attempting to load plugin from package: @nx-plugin-openapi/plugin-openapi
Failed to load plugin from node_modules: Error: Cannot find module '@nx-plugin-openapi/plugin-openapi'
Require stack:
- /Users/.../node_modules/@nx-plugin-openapi/core/src/lib/plugin-loader.js
- /Users/.../node_modules/@nx-plugin-openapi/core/src/executors/generate-api/executor.js

After:

Plugin '@nx-plugin-openapi/plugin-openapi' is not installed.
Would you like to install it using npm? (y/n) y
Installing @nx-plugin-openapi/plugin-openapi using npm...
Successfully installed @nx-plugin-openapi/plugin-openapi
Successfully loaded plugin: openapi-tools

API Changes

• loadPlugin(name, opts) now accepts an optional skipPrompt: boolean option to bypass the interactive prompt (useful for CI/programmatic usage)

Test plan

• Tests pass for all new behaviors
• Non-interactive environments skip the prompt automatically
• Package manager is logged correctly
• Stack traces only appear in debug mode
• Full test suite passes (156 tests)
• Linting passes

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