Function formatDuration

formatDuration(ms: number): string
Format milliseconds as a human-readable duration string.

Inverse of parseDuration. Produces the most natural unit for the given value, using at most two segments (e.g. "1m 30s").
Parameters
- ms: number
  Duration in milliseconds
Returns string
Human-readable duration string
Example
```
formatDuration(500);        // "500ms"
formatDuration(5000);       // "5s"
formatDuration(90_000);     // "1m 30s"
formatDuration(900_000);    // "15m"
formatDuration(3_600_000);  // "1h"
formatDuration(86_400_000); // "1d"
```
- Defined in src/utils/string-helpers.ts:293