Automated Quality Gates Pipeline for Extensions

## Description

Implement an automated quality gates pipeline for extension validation during the submission process. This pipeline will ensure extensions meet quality, security, and compatibility standards before being accepted into the registry.

## Acceptance Criteria

- Automated validation runs during submission process
- Linting checks for code quality and style
- Security scanning for vulnerabilities
- Test coverage checks and validation
- Extension manifest validation against schema
- Binary compatibility verification across platforms (Windows, macOS, Linux)
- Performance benchmarking to detect regressions
- Clear pass/fail criteria with actionable error messages
- Integration with extension submission workflow

## Implementation Notes

The quality gates pipeline should:
- Run automatically when an extension is submitted
- Provide fast feedback to extension authors
- Generate detailed reports on failures
- Support local testing before submission
- Be extensible to add new checks over time

## Parent Issue

This is part of the 3rd Party Extension Submission Process epic.

## Labels

extensions, registry, automation