Fix welcome bot trigger during onboarding flow #554

Summary

Fix onboarding flow so the welcome bot reliably triggers at the correct onboarding stage.

Problem

Welcome bot is expected to activate during onboarding, but it is not being triggered. This weakens first-use experience and onboarding guidance.

Expected Behavior

• Welcome bot starts automatically during onboarding.
• Trigger happens exactly once at intended step/state.
• User receives contextual first guidance message.

Scope

• Trace onboarding state machine and trigger conditions.
• Fix missing/incorrect trigger wiring.
• Prevent duplicate welcome triggers.
• Ensure trigger survives navigation/reload edge cases.

Acceptance Criteria

• Welcome bot consistently triggers in onboarding flow.
• No duplicate or missed welcome messages.
• Works across supported onboarding entry paths.
• Regression tests cover trigger conditions and onboarding states.