Carry server structural rejections into Radio diagnostics

The proxy now skips malformed upstream rows individually but counts
them, capped at 10,000, in the catalog metadata and the /stations
envelope (rejectedStationCount). The count never fails health policy,
so an otherwise healthy generation is still accepted. The client
validates the field, adds its own rejected rows after admission, and
reports degraded coverage when either side skipped rows. Adds an
end-to-end proxy-to-client test and aligns DATA_SOURCES.md and
CURRENT-STATE.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

changelog.d/1268-radio-issue-fix.md

@@ -1,2 +1,2 @@
-- Normalize station tags and retain valid mixed rows (asturksever, #1268).
+- Normalize station tags and retain valid mixed rows; skipped malformed rows still report degraded coverage (asturksever, #1268).
 - Correct Radio QA push-to-talk setup to target the mounted voice controller (asturksever, #1268).