Re: Tepid: selective index updates for heap relations

I should have checked and rebased before I posted v59, apologies. Here's v60 which should be clean against 1c4b1de8885.

Also fixed the following oversights:

1. CLUSTER / VACUUM FULL data loss + index staleness on SIU tables — the heap rewrite left the stale HEAP_INDEXED_UPDATED bit on flattened tuples, so readers ran the staleness test against a now-meaningless inline bitmap and dropped live rows (and returned nothing via index). Fixed by clearing the marker in reform_tuple. Hit any SIU table after a routine VACUUM FULL.

2. amcheck heapallindexed false positive — its bloom-filter fingerprint of a flagged leaf TID never matched the plain heap TID it re-derives, raising a spurious "lacks matching index tuple." Fixed by stripping the marker while fingerprinting in verify_nbtree.

3. Tooling
- pageinspect 1.14 — bt_page_items now reports the real offset in ctid/htid (was showing an inflated offset) and adds a hot_indexed column exposing the marker.
- Sentinel-safe strip — ItemPointerGetOffsetNumber/ItemPointerCompare strip bit 14 but leave the SpecToken/MovedPartitions offset sentinels untouched (a self-inflicted regression caught during development).

best.

-greg