fix: resolve pairing code rejection due to timing and platform validation issues

[mtAlves]

requestPairingCode was sending the link_code_companion_reg IQ before the server signaled readiness via pair-device, and setting creds.me before server confirmation — causing 428, 401, and 400 responses.

Changes:

• Extract sendPairingIQ from requestPairingCode to separate IQ dispatch from readiness gate logic
• Add pairingReady gate: queue requestPairingCode calls that arrive before pair-device is received, flushing them when the event fires
• Add pairingInProgress guard to reject concurrent pairing requests
• Defer creds.me assignment to after the companion_hello query succeeds, preventing reconnects from taking the login path instead of registration
• Reject pending pairing promises and reset state on socket close/error
• Fix getPlatformId return value (now consistently returns string)
• Add getPlatformDisplayName to resolve the display label for a platform type

The pairing IQ now validates companion_platform_id and companion_platform_display against server-accepted values: only browser-type platform IDs (CHROME=1..EDGE=6) are accepted; DESKTOP (7) is rejected. Custom brand names in browser[0] are preserved through DeviceProps.os (shown in WhatsApp's Linked Devices list) but are normalised to a canonical OS name in the pairing IQ itself.

[whiskeysockets-bot]

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📦 To test this PR locally:

# NPM
npm install @whiskeysockets/baileys@mtAlves/Baileys#fix/pairing-code

# Yarn (v2+)
yarn add @whiskeysockets/baileys@mtAlves/Baileys#fix/pairing-code

# PNPM
pnpm add @whiskeysockets/baileys@mtAlves/Baileys#fix/pairing-code

If you encounter any issues or have feedback, feel free to comment as well.

[devrhapp]

Uma duvida essas alteracoes vai afetar o tipo plataforma exemplo MACO, ou DESKTOP como telatado acima na descrição. Uso o valor MACO = 21 usava desktop que era o valor 14 . segundo relatos em outras prs o valor 14 nao e aceito mas pela meta.

O IQ de emparelhamento agora valida companion_platform_id e companion_platform_display em relação aos valores aceitos pelo servidor: somente IDs de plataforma do tipo navegador (CHROME=1..EDGE=6) são aceitos; DESKTOP (7) é rejeitado. Nomes de marca personalizados em browser[0] são preservados por meio de DeviceProps.os (exibidos na lista de Dispositivos Vinculados do WhatsApp), mas são normalizados para um nome de SO canônico no próprio IQ de emparelhamento.

[vielhuber]

This is important, since connecting with pairing code does not work atm.

[github-actions]

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