Fix: Lens Overview false empty on historical-only telemetry

[anilmurty]

The Lens Overview/Dashboard (default landing route) showed "No data yet — TokenJam is listening" even when the DB held a full historical spend history. This is a release blocker: it's the front door a user lands on when they open Lens to review past spend.

Summary

• Overview load() now folds /api/v1/status into the same parallel fan-out as /api/v1/cost and derives empty from the presence of real telemetry, not just active agents.
• Historical cost/tokens now render the spend/waste/health tiles even when 0 agents are active.
• Existing error-handling asymmetry preserved (/cost load-bearing, no .catch; the rest degrade individually); /status moves into the degradable set.
• Overview-component-only, offline-safe (no new external loads).

Root cause

The Overview load() gated its empty state on the count of active agents from /status and returned early before fetching /cost. On any DB where all sessions are >24h old (0 active agents) — e.g. a user upgrading and opening Lens to review historical spend — the front door read empty even though /cost returned thousands of dollars and Cost/Analytics/Optimize all rendered fine.

Fix

empty is now !hasCost && !hasAgents && !hasTraces, where hasCost is total_cost_usd > 0 || total_tokens > 0 from /cost. "No data yet" only shows when there is genuinely NO telemetry.

Tests / Verification

• node --check on the extracted <script type="module"> block: parses.
• Extended tests/unit/test_lens_ui_regression.py with test_overview_empty_gate_considers_historical_cost — asserts the buggy pattern (early return gated purely on active agents) is gone and the fix pattern (empty considers cost/history) is present, scoped to the Overview component.
• python3 -m pytest tests/unit/test_lens_ui_regression.py tests/unit/test_ui_offline.py -q → 191 passed. Offline regression test still passes (no new external loads).

What's NOT in this PR

• No change to the /cost-load-bearing vs others-.catch asymmetry — kept intact per CLAUDE.md.
• No backend/route changes — the empty-gate bug is entirely client-side.

🤖 Generated with Claude Code