Add tier-selection telemetry to UpgradeModal (Pro vs MAX choice is unobservable)

[kfarr]

Problem

checkout_started captures the final { plan, tier, source } (UpgradeModal.jsx ~line 163), but nothing before that moment is instrumented. We can see which tier a user paid for, never how they chose it:

• No event when the pricing view renders (which tiers were shown, which was default-highlighted, what initialTier/initialCycle a deep link preset)
• No event on billing-cycle toggle (monthly ↔ yearly, ~lines 438–449)
• No event distinguishing "clicked MAX card directly" from "browsed Pro first, then switched"

Both MAX-tier (/mo) conversions to date are attribution-blind on this exact question. MAX is 5× Pro ARPU — if the side-by-side presentation is doing the upsell, we should know and lean into it; if MAX buyers arrive pre-decided, the presentation work matters less. Right now the funnel can't distinguish these.

Proposed events

1. upgrade_modal_pricing_viewed — fired once per modal open when the pricing (tier-selection) view renders: { source, trigger, initialTier, initialCycle, defaultTier }
2. upgrade_billing_cycle_toggled — { from, to, source } on the monthly/yearly toggle
3. upgrade_tier_selected — fired in handleGoPro alongside the existing state change (or as an enrichment of checkout_started): include whether the chosen tier matches the deep-link preset and whether the user toggled cycle or changed tiers first

Keep checkout_started as-is for continuity; new events are additive.

Files

• src/shared/components/UpgradeModal/UpgradeModal.jsx — pricing view render, cycle toggle, handleGoPro
• src/editor/components/EditorUpgradeModal.jsx — parsePaymentHash provides initialTier/initialCycle to pass through

Related: #1892 (deep-link entries currently mis-report checkout_started source=editor — the source property these new events inherit should land after/with that fix so pricing-page deep links are attributed correctly here too).

🤖 Generated with Claude Code