feat(grasp-audit): add filter capability compliance tests

Add comprehensive GRASP-01 compliance tests for uploadpack.allowFilter
capability to the grasp-audit test suite. These tests can be run against
ANY GRASP implementation (ngit-relay, ngit-grasp, or others) to verify
filter support.

New test module: grasp-audit/src/specs/grasp01/git_filter.rs

Tests added:
- test_filter_capability_advertised: Verifies filter appears in info/refs
- test_filtered_clone_succeeds: Tests git clone --filter=blob:none
- test_filtered_fetch_succeeds: Tests git fetch --filter=tree:0

Usage:
  cd grasp-audit && nix develop -c bash test-ngit-relay.sh --mode test
  cd grasp-audit && nix develop -c cargo run -- audit -r ws://localhost:8080 -s git-filter

1 files changed, 3 insertions, 0 deletions

diff --git a/grasp-audit/src/specs/grasp01/mod.rs b/grasp-audit/src/specs/grasp01/mod.rs
index fa05f35..0a819ee 100644
--- a/grasp-audit/src/specs/grasp01/mod.rs
+++ b/grasp-audit/src/specs/grasp01/mod.rs
@@ -9,12 +9,14 @@
 //! - [`EventAcceptancePolicyTests`] - Event acceptance rules (WebSocket-only)
 //! - [`CorsTests`] - CORS headers on Git HTTP endpoints (requires git-data-dir)
 //! - [`GitCloneTests`] - Git clone operations (requires git-data-dir)
+//! - [`GitFilterTests`] - Git filter capability for partial clone (requires git-data-dir)
 //! - [`PushAuthorizationTests`] - Push authorization (requires git-data-dir)
 //! - [`RepositoryCreationTests`] - Repository creation (requires git-data-dir)
 
 pub mod cors;
 pub mod event_acceptance_policy;
 pub mod git_clone;
+pub mod git_filter;
 pub mod nip01_smoke;
 pub mod nip11_document;
 pub mod push_authorization;
@@ -24,6 +26,7 @@ pub mod spec_requirements;
 pub use cors::CorsTests;
 pub use event_acceptance_policy::EventAcceptancePolicyTests;
 pub use git_clone::GitCloneTests;
+pub use git_filter::GitFilterTests;
 pub use nip01_smoke::Nip01SmokeTests;
 pub use nip11_document::Nip11DocumentTests;
 pub use push_authorization::PushAuthorizationTests;