test(portal): regression tests + INVARIANTS rows for correctness wave 2A (7 tests, mutation-verified)

The source fixes for all five wave-2A bugs landed in the parent commit; this
adds the regression coverage, invariant-catalog rows, and the fixed-gaps
provenance that make them a merge-gated package. Every test bites: reverting
the corresponding fix hunk (tests kept) fails the named test — verbatim
assertions recorded in INVARIANTS.md "Wave 2A".

FIX 1 (head-clamp, BUG-B) — two tests in portal.test.ts:
  • a BOUNDED backfill whose toBlock is PAST the head is head-clamped so a later
    interval over the newly-finalized tail is fetched, not blind-cache-hit. The
    distinct shape vs the existing unbounded frontier-extend test: dataEnd() used
    to return backfillEnd and ignore the head, recording phantom coverage to the
    toBlock. Mutant (dataEnd = backfillEnd ?? head ?? ∞) → block 150's log lost.
  • discovery variant: a factory child created in the newly-finalized tail is
    discovered + its log fetched once the head advances (head-clamped discovery).

FIX 2 (construction-time discovery floor, BUG-A) — one test:
  • an EARLY spanning-chunk fetch issued with requiredFactoryIntervals=[] still
    runs discovery: the child log is fetched AND its address flushed. Mutant
    (floor pinned only when requiredFactoryIntervals.length > 0) → the
    strengthened INV-3 tripwire fires (through:-1) exactly where the old
    discStartIdx===undefined escape used to hide the missed discovery.

FIX 3 (extend-local neededMissing, crash-loop) — a pair:
  • an EVENT-LESS extend tail lacking a needed field over a data-bearing base is
    TOLERATED (mutant → the whole-cd check throws over the tail: blocks [101,200]).
  • an extend tail that DOES add matched rows while lacking a needed field STILL
    fails LOUD (over-tolerance guard; passes on both versions).

FIX 4 (trace/transfer receipts) — one test:
  • a trace filter with hasTransactionReceipt inserts a receipt for every matched
    trace tx. Mutant (buildTraces called without onReceipt) → zero receipts.

FIX 5 (PORTAL_FINALIZED_HEAD pin) — one test in portal-shell.test.ts (INV-9 matrix):
  • the pin survives ensureChunkSize probing the live head — an interval above the
    pin but below the live head still DELEGATES to RPC. Revert-check
    (unconditional portalHead = h) → the above-pin interval is served, not delegated.

INVARIANTS.md: INV-3/INV-9/INV-13/INV-15 rows updated (touched enforcement +
tests), INV-4's stale discStartIdx reference corrected, and five "Wave 2A"
fixed-gaps entries with the triple-blind provenance and mutation evidence.

Gates: sync-upstream.sh --test exit 0 on both 0.16.6 (160/160) and 0.15.17
(160/160); biome check portal/ 0 errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: dzhelezov