Add Tree Ring Memory

[TerminallyLazy]

Adds Tree Ring Memory to the AI Agents / Frameworks section.

Why it fits this list:

• Runs locally as a Rust CLI/TUI with project-scoped SQLite/FTS storage.
• MIT licensed and actively maintained.
• Useful for local-agent builders who need searchable, auditable, and forgettable memory lifecycle tooling.
• Uses the primary GitHub source link and keeps the description under 100 chars.

Validation performed:

• Searched existing PRs and code for Tree Ring Memory; no existing listing found.
• Verified the Tree Ring GitHub URL returns HTTP 200.
• Verified README contains exactly one Tree Ring Memory link.
• Verified the description is 58 characters.
• Ran git diff --check.