ah-nyl.14 fix: vikunja result-count header semantics (verify against source) Past Stand

Fix-verification review flagged H1's cross-check as likely wrong (CRITICAL-risk): board.go:107-131 compares the ACCUMULATED task total against the last-seen x-pagination-result-count header. If Vikunja's header means "items in the CURRENT response" (per-page) — which is the documented/likely semantics — any board >1 page makes snapshotOnce error on EVERY iteration -> reconcile aborts every pass -> no supervision, no timeouts, daemon effectively stalls at >50 tasks. Also the empty terminal page's headers are checked BEFORE the empty-page break (board.go:104-113), which under per-page semantics errors the headerless path too.

STEP 1 — establish the truth from Vikunja 2.3 SOURCE (do not guess): fetch the pagination handler from the upstream repo (github.com/go-vikunja/vikunja, tag v2.3.0 or close; the header is set in pkg/web/handler/ — search for "x-pagination-result-count"). Record the exact semantics (total vs per-page) with a file/line citation in a code comment.

STEP 2 — fix accordingly. If per-page (expected): cross-check len(page tasks) vs the header PER RESPONSE (mismatch -> error), keep x-pagination-total-pages as the page-count terminator, keep empty-page as universal terminator, keep cap-hit -> error; move the empty-page break BEFORE any header cross-checks. If genuinely total: keep the accumulated check but STILL move the empty-page break first and add the missing decisive fixtures. Either way add: multi-page fixture WITH result-count headers on every page; empty-terminal-page-with-headers fixture; headerless multi-page fixture (already exists — keep).

Constraints: scope = internal/vikunja/ ONLY (a sibling fixer works in runner/reconcile/ports concurrently). Conventions testify+culpa. Build/vet/test -race ./internal/vikunja/... only. Commit 'vikunja: fix result-count semantics per upstream source (<citation>)'; hooks bypassed; retry on index.lock; no push; no .beads/.