Closes #2650.

What changed

• add Rust FilterableValue support for Timestamp and TimeDuration
• extend TypeScript query/filter literal handling for TimeDuration
• make C# TimeDuration implement IComparable<TimeDuration>
• add client-focused coverage so the issue comment's “make sure the clients work too” ask is explicitly covered

Completeness for the #2650 comment

This PR now covers both the backend change and the client-side pieces the comment thread asked for:

• Rust backend: crates/lib/src/filterable_value.rs
  • Timestamp and TimeDuration now implement FilterableValue
• Rust client cache: sdks/rust/src/client_cache.rs
  • adds unit tests proving the Rust SDK's unique-index cache accepts both Timestamp and TimeDuration keys
• TypeScript client:
  • crates/bindings-typescript/src/lib/query.ts handles TimeDuration in query literal/comparison paths
  • crates/bindings-typescript/tests/query.test.ts covers SQL/query-side behavior
  • crates/bindings-typescript/tests/algebraic_type.test.ts covers AlgebraicType.intoMapKey(...) for Timestamp and TimeDuration, which is the key path used by the TS client cache/index machinery
• C# client:
  • crates/bindings-csharp/BSATN.Runtime/Builtins.cs gives TimeDuration the IComparable<TimeDuration> implementation required by the C# index types
  • sdks/csharp/tests~/QueryBuilderTests.cs now exercises indexed-column query expressions for both Timestamp and TimeDuration
  • crates/bindings-csharp/BSATN.Runtime.Tests/Tests.cs adds runtime/hash coverage for TimeDuration

Validation

Passed locally:

• cargo test -p spacetimedb-lib filterable_value::tests::timestamp_and_time_duration_are_filterable -- --exact
• cargo check --manifest-path sdks/rust/Cargo.toml --lib
• pnpm --filter ./crates/bindings-typescript test -- tests/algebraic_type.test.ts tests/query.test.ts

Could not run locally on this host:

• cargo test --manifest-path sdks/rust/Cargo.toml --lib ... currently pulls in a dev-dependency graph that fails here on missing native rusty_v8
• dotnet test for the C# test projects, because dotnet is not installed on this host