feat(memory): add secure user-owned memory store

[delkc]

Summary

Add the secure, user-owned foundation for Berd Memory.

• Store approved memory in readable ~/.me/me.md and ~/.me/topics/*.md files
• Respect the shared policy.json switch and deliver approved memory to supported agent sessions
• Publish a managed projection to ~/.agents/AGENTS.md without changing unrelated content
• Scope renderer writes to ~/.me, reject symlink/path escapes, and fail closed on unapproved external edits
• Share approved-content hashing and credential detection through the Rust memory core

Related issue

N/A. Bottom PR in the Memory stack.

Testing

• TypeScript typecheck, i18n, Biome, and design-system checks
• Memory preamble, publication, topic, policy, and credential tests
• Rust memory store and shared-core tests

Generated with Goose

[shellz-n-stuff]

A few issues here:

1. Why not store this encrypted with secret material in the keychain. That way it's only ever in memory cleartext rather than on disk (you can create a UI for users to edit memories manually too if you wanted)
2. The secret detection here is pretty naive. You may want to use something industry standard. Something like Titus would likely work nicely here.