Function cleanString

cleanString(raw: string): string
Returns a string that is safe to use as an MQTT topic and as a Home Assistant discovery node_id/object_id by escaping every character that is not alphanumeric or an underscore. This is a reversible, collision-free encoding: unsupported characters (including a literal hyphen) are percent-style escaped as -XX, where XX is the uppercase hex value of each UTF-8 byte. A hyphen is used as the escape sigil rather than % because Home Assistant only accepts [A-Za-z0-9_-] in discovery ids.

Because the encoding is injective, distinct inputs always produce distinct outputs, so entities whose names differ only in punctuation no longer collide onto the same discovery topic.
Parameters
- raw: string
  The string to be cleaned
Returns string
A cleaned string containing only alphanumeric characters, underscores, and hyphens
Example
```
cleanString('Living Room/Temp'); // returns "Living-20Room-2FTemp"
cleanString('Sensor#1'); // returns "Sensor-231"
cleanString('a/b'); // returns "a-2Fb"
cleanString('a b'); // returns "a-20b" (no longer collides with 'a/b')
```
- Defined in lib/utils.ts:46