fix: prevent stale change:ref listener from triggering false QR disconnect

[Adi1231234]

Fixes #127089

Problem

Two related bugs in the QR handling code:

1. The change:ref listener on AuthStore.Conn is never removed after a successful QR scan. When WhatsApp Web clears the ref during/after authentication (setting it to null/undefined), the listener fires onQRChangedEvent with an invalid ref, incrementing qrRetries past qrMaxRetries and triggering a spurious "Max qrcode retries reached" disconnect while authentication is already in progress.

2. The qrRetries counter never resets. Pre-scan QR refreshes consume retry attempts, so any post-scan QR event (even legitimate) immediately hits the limit. If linking fails and WA Web falls back to QR mode, the user gets zero retry attempts.

Changes

Three layered fixes in src/Client.js, each addressing a different aspect:

1. Reset qrRetries on loading_screen: When the loading screen fires (QR was successfully scanned and authentication begins), reset the counter to 0. If the linking fails and WA Web falls back to QR, the user gets a fresh set of retry attempts.

2. Null guard on change:ref: Skip onQRChangedEvent when ref is null/undefined. Prevents malformed QR strings (starting with "undefined,") from being emitted and counted as retry attempts.

3. Listener cleanup on change:hasSynced: Remove the change:ref listener when authentication completes (change:hasSynced on AuthStore.AppState, which is the same object as WAWebSocketModel.Socket). Prevents any stale QR events from firing after the client is fully connected.

How it was found

Production logs showed a client reaching loading 95-99% after a successful QR scan, then disconnecting 3 minutes later. The final QR event had qrLength=146 (vs normal 239), confirming the ref was the literal string "undefined". The qrRetries counter (already at 4 from normal pre-scan QR refreshes) was pushed to 5, exceeding qrMaxRetries=4.

[Adi1231234]

Hey @purpshell @BenyFilho 👋

Would any of you have a chance to review this? It fixes a pretty annoying bug where QR scan works but the client disconnects because an old listener fires.

Happy to hop on Discord or chat if anything needs clarifying!

[BenyFilho]

Hey @purpshell @BenyFilho 👋

Would any of you have a chance to review this? It fixes a pretty annoying bug where QR scan works but the client disconnects because an old listener fires.

Happy to hop on Discord or chat if anything needs clarifying!

Need user tests to validate it, and update your changes with branch main

[Adi1231234]

Hey @BenyFilho, just rebased onto the latest main, everything is up to date and CI is green.

I keep having to rebase these because other PRs get merged and create conflicts with my open ones. Would love to get them merged so I can stop chasing this 😅

About the user tests you mentioned, what exactly do you mean by that? I'm happy to help with whatever is needed to get these moving.

[BenyFilho]

Hey @BenyFilho, just rebased onto the latest main, everything is up to date and CI is green.

I keep having to rebase these because other PRs get merged and create conflicts with my open ones. Would love to get them merged so I can stop chasing this 😅

About the user tests you mentioned, what exactly do you mean by that? I'm happy to help with whatever is needed to get these moving.

Need user tests to validate it, and update your changes with branch main

[Adi1231234]

Hey @BenyFilho, thanks for the follow up!
I see that @tuyuribr approve that.
I fixed the conflicts and the CI

[Adi1231234]

Closing in favor of #201653, which consolidates this PR together with #127083 into a single, more comprehensive fix.

The new PR includes all the changes from both PRs plus additional fixes (listener cleanup, concurrency guard, atomic hasSynced check, qrRetries reset) - all validated with A/B diagnostic testing across 5 real-world scenarios.

Thanks everyone for the feedback and reviews here - it really helped shape the final solution!