feat(nimbus): smoke plumes via NOAA HMS — Nimbus PR 3

[jayrav13]

Summary

• Adds Skywatch.smoke(at:) and skywatch nimbus smoke LAT LON — pulls NOAA HMS smoke plume polygons from the public ArcGIS feature service and classifies by Light/Medium/Heavy density.
• Wires smoke into Skywatch.brief as the 6th adverse-conditions source (sigmet, airmet, pirep, convective_alert, storm_report, smoke). Smoke plumes covering the airport surface as items in adverse_conditions.items with kind: 'smoke' and a density_score (1/2/3).
• No API key required. Server-side polygon-intersect via point query — no client-side filtering, no KML parsing.

Architecture

Mirrors the existing Outlook / Alerts source patterns exactly. One source + one model + top-level convenience method + Thor subcommand + brief composer integration. The density_raw / density_level / density_score / description quartet matches Outlook's label / risk_level / risk_score / description.

Spec: docs/superpowers/specs/2026-04-30-nimbus-smoke-design.md.
Plan: docs/superpowers/plans/2026-04-30-nimbus-smoke.md.

Validation evidence

KMRY (Monterey, CA — fire-prone Pacific coast):

$ exe/skywatch nimbus smoke 36.587 -121.843 --format json
[]

KCDW (Caldwell, NJ):

$ exe/skywatch nimbus smoke 40.875 -74.282 --format text
No smoke detected at this point.

Brief composer integration:

$ exe/skywatch brief KCDW | jq '.adverse_conditions | { available, items_count: (.items | length), smoke_items: [.items[] | select(.kind == "smoke")], partial_failures: [.partial_failures[] | .source] }'
{
  "available": true,
  "items_count": 2,
  "smoke_items": [],
  "partial_failures": [
    "airmet"
  ]
}

Note: partial_failures contains airmet (the pre-existing self-intersection bug, #11) but NOT smoke — the smoke source is reachable end-to-end. Late April / early May is outside peak fire season; the empty-array case is the correct validation evidence (no smoke present + system reports cleanly + no errors + no false partial failure).

Follow-up issues already filed

• #13 — Add surface AQI from AirNow
• #14 — Add skywatch nimbus fires LAT LON
• #15 — Consider SmokeAnalysis aggregate model

Test plan

• bundle exec rspec — 414 → 445 examples, 0 failures (+31 new)
• bundle exec rubocop — 113 files, 0 offenses
• exe/skywatch nimbus smoke LAT LON — JSON + text output verified live
• exe/skywatch brief KCDW | jq '.adverse_conditions.partial_failures' — no smoke entry (source reachable end-to-end)

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