generateClientID produces control characters in WebSocket client IDs

[adnaan]

Bug

generateClientID() in internal/serve/websocket.go produces non-printable control characters in the client ID when clientCounter > 0:

func generateClientID() string {
    clientCounter++
    return time.Now().Format("20060102150405") + "-" + string(rune(clientCounter))
}

string(rune(1)) produces "\x01" (SOH control character), not "1". The intent was decimal-stringification of clientCounter; the result is the Unicode codepoint at that integer value.

Repro

2026/05/20 12:00:00 WebSocket client connected: 20260520120000-\x01 (total: 1)
2026/05/20 12:00:05 WebSocket client connected: 20260520120000-\x02 (total: 2)

The IDs do differ across counter values, so client-identity tracking still technically works — but log lines contain non-printable characters, and any code that compares client IDs against printable strings (or persists them to a log scraper that escapes non-printable chars) will see drift.

Fix

return time.Now().Format("20060102150405") + "-" + strconv.FormatUint(uint64(clientCounter), 10)

Scope

Pre-existing on lvt main (verified across the d2ffa33..f2f7e61 range — generateClientID is untouched). Flagged by claude-review on lvt#330 and pulled out as a separate issue per Phase 5 scope discipline.

Out of scope for this issue

• clientCounter is a package-level int with no mutex — a separate race-condition bug. Worth a second issue or rolled into a "WebSocketManager.generateClientID hardening" PR alongside this fix.