string-format: String.format/formatted/printf cheat sheet module (specifier anatomy, rounding vs C printf, locales, Indian lakh/crore grouping Formatter cannot do, format exceptions, %t dates, concat cost), 11 contract tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7Sr2zcoRD2watXv1G

string-format/output/05-locale.txt

@@ -0,0 +1,17 @@
+default FORMAT locale: en_US
+
+== %,.2f of 1234567.891 ==
+en-US    1,234,567.89
+de-DE    1.234.567,89
+fr-FR    1^234^567,89
+en-IN    1,234,567.89
+de-CH    1’234’567.89
+und      1,234,567.89
+
+== the bug: changing the default locale changes %.2f ==
+default (en_US)   : 1234.50
+default (de_DE)   : 1234,50
+explicit ROOT     : 1234.50
+
+== not localized: hex, NaN, Infinity ==
+ff NaN Infinity