feat(rid): screen one-hour spikes; refetch and redo-from to repair the store

RID's report sometimes carries a wrong value for one hour and corrects it
later. P.1 read 10.6 m at 2026-10-25 00:00 between 1.04 and 1.07 (RID now
says 1.06); the store kept it, because a report is re-fetched only while it
has holes, and the model issued a 10.8 m forecast for that hour.

- rid::judge / rid::screen: a reading that leaves the previous one (within
  3 h) by more than 1 m (2 m on the flashy tributaries P.76, P.77, P.81,
  P.82, P.84, P.85, P.87) while the next reading comes back near the
  previous level is a spike: not stored, a stored copy is deleted. Limbs
  and steps the next reading confirms are kept; the newest reading waits
  for the next one when it jumps more than twice the limit. On 2018-2026
  history: 16 spikes found (slipped decimals, sign flips, -5/-6/-9 m
  placeholders), no genuine change rejected.
- Every store goes through it (rid::store: run_cycle, fill-gaps, refetch).
- `ping-collector refetch FROM [TO]`: re-fetch reports regardless of holes
  (corrects revised readings, fills the discharge of level-only evening
  hours, removes stored spikes) and print the catch-up command when
  readings changed.
- `catch-up-forecasts --redo-from T`: delete the model forecasts issued
  from T on, then recompute them.
- Tests: judge/screen unit tests; a DB test of refetch, the live hold and
  the forecast deletion. Checked end to end against RID on a scratch DB.
- Docs: DATA_SOURCES (spikes, level-only hours), FLOOD_FORECASTING,
  rust/README.

rust/README.md

@@ -22,12 +22,17 @@ ping-collector serve [--listen A] [--no-analytics]
 ping-collector once [--dry-run]     # one cycle of every source; --dry-run writes nothing
                                     # and compares the RID fetch with the database
 ping-collector fill-gaps <days|all> # re-fetch RID reports with holes
+ping-collector refetch FROM [TO]    # re-fetch the RID reports of FROM..=TO (YYYY-MM-DD) even
+                                    # without holes, through the spike screening: corrects
+                                    # readings RID revised, deletes stored spikes; prints the
+                                    # catch-up-forecasts command when readings changed
 ping-collector check-db             # connect, create missing tables, row counts
 ping-collector forecast [--json] [--save] [--now T] [--rain-file F]
                                     # forecast from the database and print it
-ping-collector catch-up-forecasts [--hours N]
+ping-collector catch-up-forecasts [--hours N] [--redo-from T]
                                     # forecast the hours whose readings came late (RID's
-                                    # overnight batch) as a run then would have; default 336 h
+                                    # overnight batch) as a run then would have; default 336 h;
+                                    # --redo-from first deletes the model forecasts from T on
 ping-collector notify --dry-run     # the readings the notifier judges, and what it would send
 ```