v0.10.1

Added

• index_format_issues() validator: checks that every index.md follows the expected shape (title, summary, bullets, sibling coverage)
• gcontext share hard-rejects agents with malformed index.md files before publish
• 16 new tests for the index format validator

Fixed

• Substring bug in _mentions() that could match partial filenames as referenced siblings
• write_file warning message now explains the expected index.md shape so the agent can self-correct