Amplitude: add granular explore_* events

[hdprajwal]

Fixes #638

Summary: Splits user interactions on /data out of the catch-all page_viewed event into seven dedicated explore_* events so they can be sliced cleanly in Amplitude. page_viewed now fires only on pathname change.

Changes

• Logical changes
  • New useAmplitudeParamEvents hook mounted in AmplitudeTracker (src/app/App.tsx).
  • Seven new events sharing a path / view / entity base: explore_entity_switched, explore_view_switched, explore_sort_changed, explore_search_typed, explore_filter_changed (per-key, with filter_action), explore_detail_viewed, explore_detail_switched. Full event taxonomy is in the linked issue.
  • page_viewed dedupe in src/shared/lib/amplitude.ts now keyed on pathname only.
  • Initial-mount and pathname-change guards in the hook prevent spurious events on deep links and route transitions.
  • data_exported enriched with the same path / view / entity base for consistency. Breaking: object_type is renamed to entity on this event.
• Refactors
  • FILTER_PARAM_KEYS, deriveFilterAction, areFilterValuesEqual extracted in amplitudeFormat.ts; resolveEnumValue exported so numeric-enum filters emit readable strings.

Test Plan

1. npm run dev, accept consent, open DevTools then Network and filter for amplitude.com.
2. Navigate to /data. Confirm one page_viewed.
3. Run through each interaction: search (Enter, then clear), filter (territory + writing system in one update should emit two events), view switch, entity switch, sort change, open a card (explore_detail_viewed), click a different card (explore_detail_switched), close the panel (no event).
4. Deep-link /data?searchString=Spanish&territoryFilter=ES&view=Table. Confirm one page_viewed and zero explore_* events.
5. Navigate /data, /about, /data. Confirm one page_viewed per route change, no spurious explore_*.
6. Decline consent in the Cookie settings banner; confirm no Amplitude requests fire for any of the above.

No visual changes; screenshots not applicable.

Checklist

Summary

• Clear description of what and why
• Scope kept focused; follow-ups noted in the issue
• Set yourself as assignee
• Mention the issue (Fixes #638 )

Testing

• npm run lint
• npm run build
• npm run test (tests added for changed logic)
• npm run dev - manual walkthrough per the test plan above

[github-actions]

Cloudflare Pages preview

• Deploy URL: https://00ea95ec.lang-nav.pages.dev/lang-nav/
• Branch alias: https://pr-639.lang-nav.pages.dev/lang-nav/
  Commit: 3665614

[LuoZihYuan]

Issues & Enhancements

explore_entity_switched

1. Adjust properties {entity, from_entity, to_entity} to simply {entity, previous_entity}
2. Events involving the switch from the Language entity should always have the property previous_entity.

explore_view_switched

1. Adjust event properties {view, from_view, to_view} to simply {view, previous_view}
2. Events involving the switch from the default Cards view should always have the property previous_view.

explore_sort_changed

1. Should have included the entity property to tell which entity is currently being sorted.
2. Adjust event properties {changed_keys, sort_by, secondary_sort_by} to simply {sort}.
3. sort is now an array of variable strings representing the sorting keys. For example, sorting primarily by "Population" in descending order, and secondarily by "Name" in ascending order, should have the value ["population_desc", "name_asc"].

explore_filter_changed

1. Should have included the entity property to tell which entity is currently being filtered.
2. Decode the value of the property filter_value to the original strings for better understanding.

explore_search_typed

1. Should have included the entity property to tell which entity is currently being searched.
2. Should have included the result_count property to quickly tell if we have the data the user is searching for.
3. Add triggering logic: "Clicking on search suggestions".

explore_detail_viewed

1. Should have included the entity property to tell which entity the object belongs to.

explore_detail_switched

1. Should have included the entity property to tell which entity the object belongs to.
2. Adjust event properties {from_object_id, to_object_id} to {object, previous_object} to follow previous naming convention.