fix: keep project memory paths within the project

[lorenzozanee]

What does this PR do?

Fixes #132 by keeping memory files inside the active project when a non-Git project uses / as its worktree sentinel.

Type of change

• Bug fix
• New feature / agent
• Security tool / MCP server / Bolt plugin
• Agent skill / knowledge base
• UI / TUI improvement
• Documentation
• Refactor / performance
• CI / infrastructure

Security impact

• This PR adds or modifies tool execution (shell, file, network)
• This PR changes agent permissions or scope
• This PR modifies authentication / authorization logic
• This PR has no security impact

How did you verify it works?

Added a regression test that writes both daily and long-term memory through a real temporary project and verifies both files are under .cyberstrike in that project. bun test test/memory/project-path.test.ts, package typecheck, and Prettier checks pass.

Checklist

• bun turbo typecheck passes
• Tested locally with at least one LLM provider
• PR is focused on a single change
• No secrets, credentials, or API keys in the diff
• Breaking changes are documented (if any)