## What
Adds three privacy-safe telemetry events for the Argent Lens
design-review flow, capturing the human-decision funnel that the generic
`tool:*` path can't see (submission is an HTTP POST, and the
`await_user_selection` tool is hidden in `argent lens` CLI sessions):
- **`lens:preview_opened`** — a human loaded the preview UI (`GET
/preview/`), deduped per round.
- **`lens:round_completed`** — the human submitted their picks (once per
round, never on a resubmit).
- **`lens:round_abandoned`** — a staged round was discarded before
submit (window closed, `argent lens` exited mid-review, or the round
superseded).
## Privacy
Payloads carry only aggregate counts, booleans, durations, and the
device `platform` enum — never element names, comment text, variant
code, file paths, or raw device ids. The store emits privacy-safe
aggregate structs that are decoupled from the telemetry package;
structural assignability to the event props is enforced at the `track()`
call site (drift is a compile error).
## Event fields
- **`preview_opened`**: `round, element_count, variant_count,
is_cli_session, platform`
- **`round_completed`**: `round, element_count, variant_count,
annotation_count, element_comment_count, skipped_comment_count,
has_global_comment, is_cli_session, had_parked_await, round_duration_ms,
platform`
- **`round_abandoned`**: `round, element_count, variant_count,
had_parked_await, is_cli_session, platform`
## Testing
- Unit tests for all three events: per-round dedup, exactly-once
completion (no resubmit re-emit), abandoned vs happy-path roll, CLI
up-front open, and content-agnostic privacy assertions.
- Verified end-to-end against a live tool-server: all three events fire
with correct aggregate values and zero content leakage through the real
sanitize pipeline.
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Co-authored-by: Ignacy Łątka <latkaignacy@gmail.com>
Hubert Gancarczyk