feat(data): space weather domain — NOAA SWPC Kp index, flares, alerts (revive #141)

## Summary

#141 requested a space-weather domain and was closed, but it was never implemented — there is no SWPC/Kp/solar-flare code anywhere in the repo. Reviving with concrete scope, because space weather is a legitimate cross-domain intelligence signal (GPS/comms degradation, satellite ops, aviation polar routes, power-grid risk) that complements our existing GPS-interference and satellite feeds.

## Proposed scope

1. **Seeder**: NOAA SWPC (free, no key) — planetary Kp index, X-ray flare class, solar wind speed/density, active SWPC alerts/watches/warnings.
2. **Dashboard**: compact panel (current Kp gauge, 24h flare history, active alerts) under the World monitor; severity coloring per NOAA scales (G/S/R).
3. **MCP tool**: `get_space_weather` cache tool with freshness metadata, JMESPath support, parity entry.
4. **Cross-domain hook**: surface G3+/R3+ events into the intelligence signal stream (same path other advisories use) so briefs and country risk can reference them.

## Sources (all free)

- https://services.swpc.noaa.gov/ (JSON endpoints: Kp, flares, solar wind, alerts)
- Optional later: ESA SSA, BOM SWS for corroboration.

## Acceptance criteria

- [ ] Seeder live on the standard cadence with seed-meta freshness.
- [ ] Panel + MCP tool shipped with tests and docs.
- [ ] Severe events flow into the intelligence/advisory stream.

## Related

- #141 (original request, closed unimplemented)

No repository files or tests are named. Start by tracing existing seeders, World monitor panels, MCP cache tools, and intelligence/advisory stream integrations, then review the NOAA SWPC JSON endpoints. Done means the standard-cadence seeder, dashboard panel, MCP tool, tests, docs, freshness metadata, and severe-event signal flow all meet the listed acceptance criteria.

Written by the indexing model from the issue text.