fix(InstallWizard): reassure users when read is disabled but subscribe is active

[dionlow]

Summary

• When an integration has both read and subscribe configured for the same object, clicking Stop reading from [Object] now renders a follow-up success panel beneath the existing red callout, confirming that event subscriptions are still active and listing the subscribed events.
• The panel is gated on installation.config.content.read.objects[X].disabled === true AND installation.config.content.subscribe?.objects?.[X] being defined, so non-subscribe integrations and read-only objects are unchanged.
• No backend changes, no new public/headless API. Pure FE addition; reflects amp.yaml configuration, not delivery telemetry (footnote discloses this).

Why

A customer (Outreach) reported their end users believed the integration was broken after disabling read on a subscribe-only setup — the UI showed only "Reading is currently disabled. This object is not being synced." with no acknowledgment that events were still flowing.

Files

• New src/components/Configure/content/fields/SubscribeStillActiveBox.tsx — presentational panel, lists createEvent/updateEvent/deleteEvent/otherEvents from SubscribeConfigObject.
• Modified src/components/Configure/content/fields/ReEnableReadObject.tsx — reads subscribe config for selected object, renders the panel only when both gating conditions hold.

Test plan

• Read+subscribe object, read disabled → red "Reading is currently disabled" callout still renders, new green "Event subscriptions are still active" panel renders below it with the correct event list.
• Read-only object (no subscribe), read disabled → only the existing red callout renders. No regression.
• Subscribe-only integration, no read → ReEnableReadObject early-returns null (existing behavior); panel never mounts.
• Read enabled → only the existing green "Reading from X is enabled" success box renders.
• yarn lint clean (0 errors; pre-existing warnings only).
• yarn build passes (tsc + vite + dts).
• Visually verify event list ordering and copy match design expectations.

Out of scope / follow-ups

• First-class subscribe support in the library (own tab, toggle, headless API). This PR is a targeted fix for the customer-reported confusion only.
• Live event-delivery telemetry (lastEventAt, webhook health). Requires backend work.
• Parallel reassurance for InstalledSuccessBox when an integration is subscribe-only and skips the wizard entirely.

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