feat(inbox): capture dismissal_note in dismiss analytics event

[andrewm4894]

Summary

• Adds dismissal_note to the Inbox report action event when action_type = "dismiss" and the user typed a note in the dismiss dialog
• Truncated to 1000 chars (postgres stores up to 4000) to keep event payloads bounded
• Only attached when the trimmed note is non-empty

Why

Annika asked in Slack for a dismiss event "including their feedback" so she can read why users are dismissing inbox reports directly in PostHog instead of querying postgres_signals_signalreportartefact. We were already sending the note to the API (stored in content.note) but it wasn't on the analytics event.

Matches the precedent set by the unmerged Discuss button PR (which captures question_text truncated to 500 chars on the discuss action).

Test plan

• Dismiss a report with a reason picked but no note → event has dismissal_reason and no dismissal_note key
• Dismiss a report with a reason and a note → event has both, note value matches input, truncated at 1000 chars if longer
• Dismiss a report with whitespace-only note → no dismissal_note attached
• Snooze (i.e. reason resolves to snooze) → no dismissal-related props on the event

[greptile-apps]

_{Reviews (1): Last reviewed commit: "feat(inbox): capture dismissal_note in d..." | Re-trigger Greptile}