fix(calling): handle 409 error for keepalive

[rarajes2]

COMPLETES #< SPARK-832708 >

This pull request addresses

When Mobius answers a keepalive (device_status) with 409 Conflict, the device registration
is gone but the same user still holds an active registration elsewhere — typically calling
opened in a second browser tab, which superseded this one. Previously a 409 fell through to the
default branch of handleRegistrationErrors, so the SDK re-registered. That unregistered the
other tab, which then re-registered and unregistered this one, producing a registration
ping-pong between tabs.

by making the following changes

A 409 on keepalive is now a hard stop: the keepalive worker is terminated, no re-registration is
attempted, the Mobius WebSocket is closed, and the app is notified that its session was
superseded.

• register.ts — the KEEPALIVE_FAILURE branch short-circuits to a new
  handle409KeepaliveFailure before handleRegistrationErrors runs, so no retry, failover, or
  restore path can execute. The worker is stopped up front (before waiting on the shared mutex)
  so no further keepalive can be sent.
• performRegistrationDownCleanup → performHardStopCleanup(caller, hardStop), now shared with
  the 409 path. A HardStop discriminated union (registration/types.ts) makes it impossible to
  signal a superseded session without the LineError the consumer receives, and its
  HARD_STOP_REASON values double as the log label. Teardown is unchanged: timers cleared,
  transient flags and failover cache reset, status INACTIVE, WebSocket closed with the existing
  permanent code {code: 3050, reason: 'done (permanent)'}.
• Observability: submits the existing KEEPALIVE_ERROR / KEEPALIVE_FAILURE registration metric
  and calls uploadLogs().

Public API (additive)

• New LINE_EVENTS.SESSION_SUPERSEDED = 'session_superseded', typed in LineEventTypes as
  (error: LineError) => void.
• New ERROR_TYPE.SESSION_SUPERSEDED and ERROR_CODE.CONFLICT = 409.
• For backward compatibility unregistered still fires first, followed by session_superseded
  with the error. Line.lineEmitter re-emits it through the same guarded branch as error.

No existing event, payload, or status transition changed. Keepalive 404 / 429 / 5xx and the
registration, restoration, failover, and failback paths are untouched — the short-circuit is
scoped to the keepalive worker's failure branch only.

Notes

The LineError message comes from a new SESSION_SUPERSEDED_MESSAGE constant rather than
Mobius's data.message: the keepalive worker's failure envelope forwards only headers/status, and
adding the response body would have silently changed the 403 device-limit branch in
handleRegistrationErrors. Detection relies solely on the status code.

Change Type

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tooling change
• Internal code refactor

The following scenarios were tested

Vidcast - https://app.vidcast.io/share/d6bda2af-24a9-4cee-ab69-d9a2da283aa3

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  • Feature
  • Defect fix
  • Tech Debt
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I certified that

• I have read and followed contributing guidelines
• I discussed changes with code owners prior to submitting this pull request
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• All existing and new tests passed
• I have updated the documentation accordingly

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[chatgpt-codex-connector]

End active calls when the session is superseded

When a second tab or device supersedes a registration during an active call, this path marks the line inactive and disconnects its transport without ending the call retained by CallManager. Unlike handleRegistrationDownEvent(), which explicitly calls activeCall?.end(), the 409 path leaves the call, media connection, and call timers alive even though no further Mobius events can arrive, so consumers may continue displaying a stale established call. End the active call(s) before performing this hard-stop cleanup.

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