fix(ssr): stop content-card forcing always-on scrollbars; add tmp/ scratch dir

content-card used `overflow-scroll`, which renders scrollbar tracks even
when the content fits — visible as superfluous bars around the admin chart
cards. Switch to `overflow-auto` so scrollbars only appear when content
genuinely overflows (e.g. wide data tables still scroll).

Also add a gitignored ./tmp/ scratch directory (tracked via .gitkeep) and
document in AGENTS.md that temp files belong there.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -51,3 +51,6 @@ sysco-poller/**/*.csv
 .tmp/**
 playwright-report/**
 test-results/**
+# Scratch dir for temp files (screenshots, logs, etc.); keep the dir, ignore contents
+/tmp/*
+!/tmp/.gitkeep