Validate entries in jobPorts() function

[Kunal1522]

Description

The jobPorts() function reads .func/runs/ to find running instances but doesn't validate entries. It could return files or non-port directories as "ports".

Current Behavior

Returns all entries without checking if they're valid port directories:

// TODO: validate it's a directory whose name parses as an integer?

Proposed Fix

Add filtering to only include directories with integer names (valid ports):

if !f.IsDir() || !isValidPort(f.Name()) {
    continue
}

This matches the validation already in cleanupJobDirs().
/kind cleanup

[Kunal1522]

/assign