docs: note orRedirect catch-type change in UPGRADING, add exception rule of thumb

orRedirect() is the only throw whose catch type changed in 3.0.0
(RuntimeException to CallerException), so UPGRADING's silent-changes list
gets one bullet with the working catches. ai-reference now states the
exception model in one line: RuntimeException from orThrow() is the only
type to catch in normal operation, everything else means code to fix.

Author: daveedis

UPGRADING.md

@@ -77,6 +77,11 @@ Full lists of what changed per release: [CHANGELOG.md](CHANGELOG.md).
 > exit codes now see the failure
 > - `pregReplace()` with an invalid pattern throws an exception naming your
 > file and line (was a PHP warning and a null result)
+> - `orRedirect()` with headers already sent throws CallerException (an
+> InvalidArgumentException subclass) instead of RuntimeException - the only
+> exception whose catch type changed in this release. A specific
+> `catch (RuntimeException)` around it no longer matches; `catch (Exception)`
+> and `catch (Throwable)` work in both versions
 > - Constructor and `new()` no longer accept a `$properties` array (carried
 > an internal flag; nothing outside the class used it)
 

docs/ai-reference.md

@@ -293,6 +293,9 @@ print_r($str);        // shows rawData (original value) + one-time help() hint
   braces in a string (`$str->trim`, `"$str->trim()"`). Page continues;
   expression yields an empty SmartString.
 
+Rule of thumb: RuntimeException (from `orThrow()`) is the only type to catch
+in normal operation - everything else means code to fix.
+
 ## Gotchas Quick Reference
 
 - Wrapping output in `htmlspecialchars()` double-encodes (`'` in