Restrict the legacy IDE-version override to generation endpoints so
catalog and other passthrough requests keep their original User-Agent
and metadata.ideVersion, letting newer Antigravity releases see current
models like Gemini 3.7 Flash in the MITM selector.
Fixes#3414
Merge the complete generated .next-cli-build/server tree into the
packaged CLI after the standalone copy, since Next's standalone output
is trace-pruned and can omit route modules (e.g. /api/v1/messages) or
chunks loaded dynamically. Add a post-copy integrity check for the
required API route artifacts so an incomplete package fails during
pack:cli instead of at runtime.
Fixes#2945
Matt Van Horn