#886 swamp serve writes grant model files to ./models/swamp/grant/ instead of .swamp/

When running swamp serve in an orchestrator repository and adjusting grants, grant model files are written to ./models/swamp/grant/. This was noticed via git status showing untracked files in that directory.

Raised in Discord and was asked to ticket it, as the consensus suggestion is that these files should live under .swamp/ rather than ./models/swamp/grant/, keeping them out of the user's source tree.

Steps to Reproduce

1. Run swamp serve in a repository that uses grants.
2. Adjust grants or similar configuration.
3. Run git status — observe untracked files under ./models/swamp/grant/.

Expected Behavior

Grant-related files generated by swamp serve should be written to .swamp/ (or another location that is clearly internal/managed), not to ./models/swamp/grant/ which sits in the user's source tree and shows up as untracked in version control.

Actual Behavior

Files appear under ./models/swamp/grant/, mixing swamp-managed state with user-authored model definitions.

Additional Context

Not familiar enough with the implications of these files yet to comment definitively on the correct location, but happy to test, reproduce, and provide further details if needed.