fix(ops): stop feed alert firing on orphaned and static feeds

[robertleifke]

numo-feed-alert fires every minute on two feeds that nothing reads. Same
self-correcting shape as #77's zero-open-interest exit: a condition re-evaluated
every run, not a disabled timer.

Why they are stale

• Market 1 moved to the static stable feed on 2026-09-09; market 2 to the static
  cNGN feed at the SRM cutover on 2026-09-10. Neither monitored feed is the spot
  feed of any SRM market any more.
• The publisher (numo-feeds) was retired 2026-09-22 after its relayer ran out of
  gas, so the staleness is now permanent and expected.

Two skips, both narrow

1. Orphan — feed is not the spot feed of any SRM market, read from OraclesSet
   logs (spotFeeds is internal; latest event per market wins). Re-point a market
   at one of these and its alert comes straight back on the next run.
2. Static — feed prices via getSpot() but never writes spotDetail, so
   now - 0 reads as ~1.8e9 seconds stale forever. Only applies when the stored
   price is 0 and the feed still answers getSpot().

A live feed that was never published has no timestamp and cannot price, so it
is not classified static and still alerts.

Verified against Base mainnet

Path	Result
Orphaned feed	quiet skip, exit 0
Live-but-static feed (0x507D6456…, returns 1e18)	quiet skip, exit 0
Live feed genuinely broken (forced 0x41512C6a… into the live set)	alerts, exit 1
Feed-lookup itself fails (RPC down)	alerts loud, exit 1

The third row is the one that matters: the dead cNGN feed has a stale price in
slot 6 but reverts getSpot(), so it is correctly not silenced.

SEL_GET_SPOT is 0x2b37269c from cast sig "getSpot()", not written by hand —
the first attempt at this selector was wrong and would have failed silently by
classifying every feed as non-static.