fix(taskfile): quote fmt-check cmd so YAML doesn't parse inner colon as a map

go-task 3.51.1 read the unquoted scalar 'echo "gofmt: files..."' as a
key:value mapping, failing every task with 'invalid keys in command' and
blocking the whole quality gate (not just the acceptance suite). Wrap the
command in an explicit double-quoted YAML scalar.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Taskfile.yml

@@ -24,7 +24,7 @@ tasks:
   fmt-check:
     desc: Fail if any file is not gofmt-clean.
     cmds:
-      - test -z "$(gofmt -l .)" || { echo 'gofmt: files need formatting:'; gofmt -l .; exit 1; }
+      - "test -z \"$(gofmt -l .)\" || { echo 'gofmt: files need formatting:'; gofmt -l .; exit 1; }"
 
   vet:
     desc: go vet.