docs: surface solar provenance in the nav, drop internal integration log

solar-conditions-provenance.md was in the tree but absent from the
mkdocs nav and unlinked from anywhere, so it never appeared on the docs
site. Added under a Project section and linked from the solar command
entry, where a reader would look for it.

Removes the kg7qin PR integration log — an internal development record
that was excluded from the docs build but still shipped in the repo —
along with the now-dead exclude glob.

docs/command-reference.md

@@ -411,6 +411,10 @@ solar
 - HF band conditions (Open/Closed/Marginal)
 - Solar activity summary
 
+Data comes from HamQSL and NOAA SWPC. For the provenance of the underlying
+`modules/solar_conditions.py` implementation, see
+[Solar conditions rewrite provenance](solar-conditions-provenance.md).
+
 ---
 
 ### `solarforecast` or `sf`