Document SPC outlook support

docs/internal/sources.md

@@ -28,6 +28,7 @@ Current drivers:
 | `openmeteo_observation` | `observation` | `raw.openmeteo.current.v1` |
 | `openmeteo_forecast` | `forecast` | `raw.openmeteo.hourly.forecast.v1` |
 | `openweather_observation` | `observation` | `raw.openweather.current.v1` |
+| `spc_convective_outlook` | `outlook` | `raw.spc.convective_outlook.v1` |
 
 ## Boundaries
 
@@ -40,7 +41,7 @@ Current drivers:
 
 ## Config Fields Used
 
-All current source drivers use feedkit `HTTPSource`.
+Most source drivers use feedkit `HTTPSource`.
 
 Required params:
 
@@ -56,12 +57,18 @@ Optional params:
 OpenWeather observation sources additionally require the configured URL to use
 metric units. This is enforced by `internal/providers/openweather`.
 
+The SPC convective outlook source is a multi-document poll source rather than a
+single-URL `HTTPSource`. It requires `latitude`, `longitude`, and `user_agent`;
+accepts optional `location_id`, `location_name`, `geojson_urls`,
+`discussion_urls`, and `rss_url`; and supports `http_timeout` and
+`http_response_body_limit_bytes`.
+
 Source-level `kinds`, when configured, are validated against the source's
 advertised `Kinds()`.
 
 ## External Adapters Used
 
-Sources use feedkit's HTTP helper for:
+Most sources use feedkit's HTTP helper for:
 
 - request construction;
 - `User-Agent` and `Accept` headers;
@@ -71,11 +78,15 @@ Sources use feedkit's HTTP helper for:
 
 NWS helpers parse NWS timestamps. Open-Meteo helpers parse provider-local times
 with timezone or UTC-offset data. OpenWeather helpers enforce metric-unit URLs.
+SPC helpers define Day 1-3 product metadata, parse GeoJSON timestamps, extract
+cleaned print-page discussion text, and parse optional RSS metadata.
 
 ## State
 
-HTTP conditional validators are held in each source instance. They are not
-persisted across process restarts.
+HTTP conditional validators are held in each single-document HTTP source
+instance. They are not persisted across process restarts. The SPC outlook source
+keeps only a source-local hash of the most recent complete required product
+bundle and emits no event when a later complete bundle is unchanged.
 
 ## Failure Behavior
 
@@ -88,12 +99,18 @@ to default ID/effective-time behavior from feedkit source helpers.
 
 Unchanged conditional responses return no events and no error.
 
+The SPC outlook source fetches all configured Day 1-3 GeoJSON products and print
+pages atomically. If any required GeoJSON or print-page request fails, the poll
+returns an error and emits no partial bundle. RSS is fetched only when `rss_url`
+is configured.
+
 ## Tests To Inspect
 
 - `internal/sources/builtins_test.go`
 - provider source tests under `internal/sources/nws`
 - provider source tests under `internal/sources/openmeteo`
 - provider source tests under `internal/sources/openweather`
+- provider source tests under `internal/sources/spc`
 - provider helper tests under `internal/providers`
 
 ## Invariants