Add Tree Ring Memory plugin

[TerminallyLazy]

Adds Tree Ring Memory as a Claude Code plugin marketplace entry under Workflow Orchestration.

Tree Ring Memory provides local-first agent memory lifecycle guidance for recall, concise memory capture, evidence records, audit, consolidation, and explicit forgetting. The plugin source is the public wrapper repo: https://github.com/TerminallyLazy/tree-ring-memory-claude-plugin

Validation performed:

• claude plugin validate .claude-plugin/plugin.json --strict in the wrapper repo passed
• claude plugin validate .claude-plugin/marketplace.json --strict in the wrapper repo passed
• Wrapper repo GitHub Actions validation passed
• claude plugin validate .claude-plugin/marketplace.json in this repo passed with the existing metadata.homepage warning
• Duplicate plugin-name check passed
• git diff --check passed