Support CLAUDE.local.md output for folder context files

[github-actions[bot]]

Originally posted as issue #967 by @cwebbi1
#967

Is your feature request related to a problem? Please describe.
When using git worktrees for parallel Claude Code development, each worktree shares the same tracked files (including CLAUDE.md) but needs its own isolated context. Currently, claude-mem's folder CLAUDE.md generation writes to CLAUDE.md, which is tracked by git. This causes conflicts when running multiple worktrees with different goals, since they all share the same CLAUDE.md through git history.

Describe the solution you'd like
Add a configuration option to specify the output filename for folder context files:

{
  "CLAUDE_MEM_FOLDER_CLAUDEMD_FILENAME": "CLAUDE.local.md"
}

Claude Code natively supports CLAUDE.local.md as a gitignored, per-directory memory file. Writing to this instead of CLAUDE.md would allow:
- Each worktree to have its own isolated memory timeline
- No git conflicts between worktrees
- Clean separation between team-shared instructions (CLAUDE.md) and auto-generated session history (CLAUDE.local.md)

Describe alternatives you've considered
- Post-generation hook to rename CLAUDE.md to CLAUDE.local.md (hacky, race conditions)
- Disabling the feature entirely and manually maintaining CLAUDE.local.md (loses the auto-timeline benefit)
- Adding CLAUDE.md to .gitignore (loses ability to share project instructions with team)

Additional context
Git worktrees are a popular pattern for running multiple Claude Code instances in parallel (see incident.io blog, ccswitch, ccswarm). Native support for CLAUDE.local.md output would make claude-mem fully compatible with this workflow.