chore: fix Justfile refs (#2672)

Turns out using {{X}} in a global doesn't get interpolated by Just. This
resulted in files like the literal `{{CONSOLE_ROOT}}/foo/bar`, which
don't exist, being used for dependency checks, triggering rebuilds on
every invocation.

In particular this would trigger proto rebuilds and console rebuilds,
the latter of which was quite time consuming :\

Justfile

@@ -8,10 +8,10 @@ TIMESTAMP := `date +%s`
 SCHEMA_OUT := "backend/protos/xyz/block/ftl/v1/schema/schema.proto"
 ZIP_DIRS := "go-runtime/compile/build-template go-runtime/compile/external-module-template go-runtime/compile/main-work-template internal/projectinit/scaffolding go-runtime/scaffolding jvm-runtime/java/scaffolding jvm-runtime/kotlin/scaffolding"
 CONSOLE_ROOT := "frontend/console"
-FRONTEND_OUT := "frontend/console/dist/index.html"
+FRONTEND_OUT := CONSOLE_ROOT + "/dist/index.html"
 EXTENSION_OUT := "frontend/vscode/dist/extension.js"
 PROTOS_IN := "backend/protos/xyz/block/ftl/v1/schema/schema.proto backend/protos/xyz/block/ftl/v1/console/console.proto backend/protos/xyz/block/ftl/v1/ftl.proto backend/protos/xyz/block/ftl/v1/schema/runtime.proto"
-PROTOS_OUT := "backend/protos/xyz/block/ftl/v1/console/console.pb.go backend/protos/xyz/block/ftl/v1/ftl.pb.go backend/protos/xyz/block/ftl/v1/schema/runtime.pb.go backend/protos/xyz/block/ftl/v1/schema/schema.pb.go {{CONSOLE_ROOT}}/src/protos/xyz/block/ftl/v1/console/console_pb.ts {{CONSOLE_ROOT}}/src/protos/xyz/block/ftl/v1/ftl_pb.ts {{CONSOLE_ROOT}}/src/protos/xyz/block/ftl/v1/schema/runtime_pb.ts {{CONSOLE_ROOT}}/src/protos/xyz/block/ftl/v1/schema/schema_pb.ts"
+PROTOS_OUT := "backend/protos/xyz/block/ftl/v1/console/console.pb.go backend/protos/xyz/block/ftl/v1/ftl.pb.go backend/protos/xyz/block/ftl/v1/schema/runtime.pb.go backend/protos/xyz/block/ftl/v1/schema/schema.pb.go " + CONSOLE_ROOT + "/src/protos/xyz/block/ftl/v1/console/console_pb.ts " + CONSOLE_ROOT + "/src/protos/xyz/block/ftl/v1/ftl_pb.ts " + CONSOLE_ROOT + "/src/protos/xyz/block/ftl/v1/schema/runtime_pb.ts " + CONSOLE_ROOT + "/src/protos/xyz/block/ftl/v1/schema/schema_pb.ts"
 
 _help:
   @just -l