feat: flat spell frontmatter, full source-book titles, drop circle

Parser reads human-friendly flat keys (range, targets, castingTime, overcast
list, threshold/successes, ...) and expands them to SpellData; fixes
[object Object] range, empty targets/casting time and blank overcast rows.
SOURCE_BOOKS ids now match vault slugs and show full book titles.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/logic/spell-cast.ts

@@ -230,7 +230,6 @@ async function renderCastCard(
     rolls: rollsHtml,
     mode,
     school: spell.system.school ?? '',
-    circle: (spell.system as any).circle ?? 0,
     outcome: { success },
     costs,
     damage,