Add SwiftLint as an advisory CI-only lint job (no Xcode plugin dependency) (#1361)

* Add SwiftLint as an advisory CI-only lint job (no Xcode plugin dependency)

* Harden the advisory lint job and exclude build dirs from local runs

The lint job runs a third-party container image, so drop its token to
read-only, stop actions/checkout from persisting credentials into the
workspace the container can read, and pin the image by digest as well
as tag (tags are mutable). Also add an excluded: list to .swiftlint.yml
so local swiftlint runs don't drown in .build/DerivedData artifacts —
CI checkouts are fresh, so this only affects working trees.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.swiftlint.yml

@@ -0,0 +1,33 @@
+# Build artifacts and generated sources; keeps local `swiftlint` runs clean
+# (CI checkouts are fresh, so this only matters in a working tree).
+excluded:
+  - .build
+  - .swiftpm
+  - .DerivedData
+  - DerivedData
+  - build
+  - localPackages/*/.build
+
+disabled_rules:
+  - line_length
+  - type_name
+  - identifier_name
+  - statement_position
+  - implicit_optional_initialization
+  - force_try
+  - vertical_whitespace
+  - for_where
+  - control_statement
+  - void_function_in_ternary
+  - redundant_discardable_let  # SwiftUI breaks without it
+  # To be enabled as we fix the issues
+  - trailing_whitespace
+  - cyclomatic_complexity
+  - function_body_length
+  - function_parameter_count
+  - type_body_length
+  - file_length
+  - large_tuple
+  - force_cast
+  - multiple_closures_with_trailing_closure
+  - nesting