docs: lsim.rid.go.th is unreachable, not geo-blocked

Probed from a Thai consumer ISP (AIS Fibre): DNS resolves but ICMP and
ports 80/443/8080 are filtered, while app.rid.go.th answers in 0.27 s
over the same connection. Correct the earlier note that assumed the
timeout was a foreign-network block, and stop pointing the dam-feature
follow-up at a host that cannot be reached.

docs/FLOOD_FORECASTING.md

@@ -509,8 +509,10 @@ event-peak amplitude (−0.11 → −0.03 m on the Sep 2024 event), and `rise_da
 opt-in via `--dam` on the training CLI, `scripts/backtest_render.py --dam`,
 and the `rise_rain_dam` / `rise_dam` harness variants). The collector keeps
 accruing daily rows; revisit post-monsoon when the 2026 season adds dam-era
-flood events — an intraday scrape (the lsim.rid.go.th source, reachable only
-from Thai networks) would remove the publication-lag objection entirely.
+flood events. Removing the publication-lag objection needs an *intraday*
+reservoir source; the obvious candidate, `lsim.rid.go.th`, is unreachable
+even from a Thai consumer ISP (see `docs/DATA_SOURCES.md`), so that remains
+an open search.
 
 **Shipped from the same work:** the HII gap-fill merge in the data loader
 (`fill_from_hii`, +9,341 h at P.81, +682 h at P.92, +810 h at P.20) is