Session memory should not be scoped to working directory path

Currently, Claude Code's auto-memory system stores memories under a path derived from the working directory (e.g. .claude/projects/-home-user-scm-myproject/memory/). This means:

• Moving or renaming a project directory silently orphans all accumulated memory.
• Switching to a different workspace for the same work starts a blank session with no prior context.
• There is no way to resume a session's memory from a different directory without manually copying files.

Expected behaviour: Memory should be associated with a named session or project identifier that the user controls, not the filesystem path. This would allow memory to survive project moves, renames, and workspace switches.

Suggested fix: Allow users to assign a named project ID (e.g. in CLAUDE.md or a config flag) that is used as the memory key instead of the directory path. The directory-derived key could remain as the default for backwards compatibility.