add four design themes + syntax tokens to theme pipeline

SurfaceTokens gains seven syntax-role fields (keyword, type,
string, number, comment, method, punct). Theme loader parses
the syntax: YAML block and injects values into the surface
override layer. Resolver defaults map syntax roles to semantic
colours so themes without explicit syntax blocks still compile.

Four new theme YAMLs (clide, midnight, paper, terminal) replace
summer-night. Palette keys mapped to the existing semantic layer;
syntax values pass through directly. Goldens regenerated for the
14→font-size change.

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

pubspec.yaml

@@ -6,7 +6,7 @@
 # `dart compile exe` produces a lean static binary.
 #
 # The Flutter desktop UI lives under `app/` as a separate package that
-# depends on this one via a path: dependency. See ADR 0005 for the
+# depends on this one via a path: dependency. See D-005 for the
 # layout rationale.
 #
 # Version is mirrored from project.yaml on every bump. project.yaml is