chore: make contributor tooling work; fix drifted docs (#648)

- mypy.ini parses again (multi-line exclude and inline value comments made
  mypy reject the file); the mypy pre-commit hook is manual-only until the
  ~500 existing errors in src/ are paid down, and CONTRIBUTING says so
- .gitignore: ignore all of config/ except the templates (ytm_auth.json and
  others weren't ignored)
- .gitattributes: LF for .sh and .service
- claude-code-review: skip fork PRs, which have no secrets
- check_system_compatibility.sh: 3.13 supported, <3.10 an error
- docs/scripts drift: emulator guide, README API Metrics, route count,
  docs index, scripts README; pyflakes nits in dev scripts

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

mypy.ini

@@ -1,6 +1,11 @@
 [mypy]
 # Mypy configuration for LEDMatrix
 
+# What a bare `mypy` checks. ini values can't span lines or carry trailing
+# comments -- this file used to have both, so mypy refused to read it at all.
+files = src
+exclude = (^|/)(test|__pycache__)/
+
 # Python version
 python_version = 3.10
 
@@ -25,11 +30,11 @@ warn_unreachable = True
 # Strict optional checking
 strict_optional = True
 
-# Disallow untyped definitions
-disallow_untyped_defs = False  # Set to True once all code is typed
+# Disallow untyped definitions (set to True once all code is typed)
+disallow_untyped_defs = False
 
-# Disallow untyped calls
-disallow_untyped_calls = False  # Set to True once all code is typed
+# Disallow untyped calls (set to True once all code is typed)
+disallow_untyped_calls = False
 
 # Check untyped definitions
 check_untyped_defs = True
@@ -96,10 +101,3 @@ ignore_missing_imports = True
 [mypy-spotipy.*]
 ignore_missing_imports = True
 
-# Exclude test files and generated files
-exclude = (?x)(
-    ^test/.*|
-    ^.*/__pycache__/.*|
-    ^.*\.pyc$
-)
-