Echo v2.2.1

Crash hardening and path safety. Second 2.2 slice. Failure model unchanged. No new language syntax.

Host / builtins:

• Reject oversized integers so parse, print, diagnostics, ask, exit, repeat / pad, rangeList, and regex {n} counts cannot crash the interpreter
• Reject unbounded recursion on deeply nested expressions and function calls (RecursionError → Echo abort)
• Reject NUL bytes and non-HTTP URLs so host builtins / httpGet cannot crash
• Reject cyclic symlinks so file builtins cannot crash with Python traceback
• removeFile / removeTree no longer delete through symlinks; removeTree("") and removeTree("..") cannot wipe the working directory or parent
• exit() rejects status values that do not fit in a C long
• order() stays safe when the comparator mutates the list; string allocation failures in repeat / pad abort cleanly

Language / tooling correctness:

• Unescape switch string arms and hash-literal keys so escaped literals match and elang fmt stay consistent
• Keep elang fmt from rewriting overflowed floats as inf, or breaking strings that contain quotes
• Lexer rejects deeply nested interpolations and interpolation quotes that end with a backslash instead of crashing
• CLI rejects unreadable source files instead of crashing
• Formatter string-wrap path is valid on Python 3.10 / 3.11 (no backslash inside f-string expressions)