Disable automatic CLAUDE.md updates by default

[cheapsteak]

Problem

The spec-kit tool automatically updates the root CLAUDE.md file with technology information, and this behavior is quite annoying because:

1. Repeated additions: It repeatedly adds the same technologies to the file, creating duplicate entries
2. Unwanted modifications: Users may not want their CLAUDE.md file modified automatically as part of the spec workflow
3. Noisy diffs: These automatic changes create noise in git diffs and can accidentally get committed

Current Behavior

When running spec-kit commands, it modifies the root CLAUDE.md file to add entries like:

## Active Technologies
- Python 3.12 (backend/ingest), TypeScript (frontend) ...

These entries accumulate and repeat, cluttering the file.

Requested Change

Please make the automatic CLAUDE.md updates opt-in rather than opt-out. Options could include:

1. Add a flag like --update-claude-md that must be explicitly passed to enable this behavior
2. Add a configuration option in the spec-kit config to control this behavior (default: disabled)
3. At minimum, prevent duplicate entries from being added

Workaround

Currently users must manually revert changes to CLAUDE.md after running spec-kit commands.