refactor: consolidate duplicate utility functions (#12439)

* refactor: consolidate duplicate utility functions

- Add escapeRegExp to src/utils.ts and remove 10 local duplicates
- Rename bash-tools clampNumber to clampWithDefault (different signature)
- Centralize formatError calls to use formatErrorMessage from infra/errors.ts
- Re-export formatErrorMessage from cli/cli-utils.ts to preserve API

* refactor: consolidate remaining escapeRegExp duplicates

* refactor: consolidate sleep, stripAnsi, and clamp duplicates

src/agents/bash-tools.shared.ts

@@ -146,7 +146,10 @@ function safeCwd() {
   }
 }
 
-export function clampNumber(
+/**
+ * Clamp a number within min/max bounds, using defaultValue if undefined or NaN.
+ */
+export function clampWithDefault(
   value: number | undefined,
   defaultValue: number,
   min: number,