fix(runtime-fallback): use precise regex patterns for status code matching

Replace word-boundary regex with stricter patterns that match

status codes only at start/end of string or surrounded by whitespace.

Prevents false matches like '1429' or '4290'.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/runtime-fallback/constants.ts

@@ -29,9 +29,9 @@ export const RETRYABLE_ERROR_PATTERNS = [
   /overloaded/i,
   /temporarily.?unavailable/i,
   /try.?again/i,
-  /\b429\b/,
-  /\b503\b/,
-  /\b529\b/,
+  /(?:^|\s)429(?:\s|$)/,
+  /(?:^|\s)503(?:\s|$)/,
+  /(?:^|\s)529(?:\s|$)/,
 ]
 
 /**