docs(scratch): handoff — триаж #5 закрыт, ревью APPROVED, идёт приёмка

- Зачем:
  - зафиксировать состояние конвейера #5 перед долгой живой приёмкой,
    чтобы новая сессия продолжила без потери контекста.
- Что:
  - в handoff добавлена дельта 23:10: обе находки FIXED (фрагменты ID
    с SHA-256-цепочкой), перепроверка линией B — APPROVED;
  - обновлено состояние стенда: им владеет сценарий приёмки;
  - в .scratch/issue5-run добавлены свежие отчёты, перепроверка и
    сценарий приёмки acceptance-issue5.sh.
- Проверка:
  - git show --stat; лог приёмки — до строки SCRIPT_EXIT_CODE=.

.scratch/issue5-run/recheck-focus-issue5.md

@@ -0,0 +1,70 @@
+# Narrow recheck: issue #5 fix round (findings CODE-1, CODE-2 only)
+
+You are review line B (code quality) doing a NARROW recheck after a fix
+round. Fresh session, no executor history. Do NOT modify sources, git
+state, or permanent environment. You may read anything and run focused
+tests (pytest of specific files is fine).
+
+Repo: /home/dementev/sources/clickstream-ch-kafka-superset-demo, branch
+feature/mentee-path. Scope: ALL uncommitted working-tree changes
+(git status / git diff vs HEAD), but ONLY re-verify the two findings below.
+This is NOT a full re-review — do not open new lines of critique unless
+you find a defect introduced BY the fix itself.
+
+Context files (same directory as this file):
+- review-issue5-code.md — your line's original full report (CODE-1..CODE-2)
+- report-issue5.md — executor's report; section "## Triage round 1"
+  describes the fix design and measurements
+- mandate-issue5.md — original executor mandate (invariants)
+
+## Finding CODE-1 (was High, == TASK-1): manifest payload ceiling
+
+Original defect: cumulative manifest embedded exact click_id/uid sets,
+~0.81 MB already on the reference world, Kafka 1 MiB default message limit
+not overridden → save fails after ~1 more next-day; storage O(history) in
+a SINGLE message.
+
+Executor's claimed fix: exact ID sets moved out of the manifest into
+content-addressed chunks (≤10,000 IDs each, SHA-256 chain, separate compact
+topic generator_startup_history_counter_chunks); main manifest keeps totals
++ rolling checksums + chain head/count; next-day appends only new-ID
+chunks, never rewrites or scans history; explicit 900,000-byte pre-send
+guard with Russian error on both manifest and chunks.
+
+Verify:
+1. The single-message ceiling is genuinely gone: no code path serializes
+   the full ID history into one Kafka message (check import, backfill AND
+   next-day paths).
+2. Chunk chain integrity: hash chain actually validated on read; chain
+   head/count in manifest actually checked; a broken/missing chunk fails
+   loudly (Russian error), not silently.
+3. next-day is still O(new day): no full chunk-chain scan or historical
+   chunk rewrite on the incremental path.
+4. Exactness preserved: uniqExact comparison against ClickHouse still uses
+   exact counts; the required incremental-vs-full-recompute equality test
+   still genuinely compares incremental vs full recompute after the
+   restructure (not weakened to pass).
+5. The 900,000-byte guard is real (applied before send on every producer
+   path for these payloads) and its failure mode is explicit.
+6. Boundary-ID sourcing from generator state (active visits + users with
+   visits, pre-created unused users excluded) does not break determinism
+   or the day-boundary duplicate handling the tests claim.
+
+## Finding CODE-2 (was Low): write ordering
+
+Original defect: next-day saved state BEFORE manifest (import did reverse),
+widening the half-advanced window.
+
+Verify: order is now chunks → manifest → state on ALL three paths (import,
+backfill, next-day), and the two-day test actually asserts it.
+
+## Report
+
+Write full report (English) to recheck-issue5-code.md in this same
+directory. Structure: per finding — RESOLVED / NOT_RESOLVED / REGRESSION
+(new defect introduced by the fix, with severity, file:line, scenario).
+End with VERDICT: APPROVED (both resolved, no regressions) or
+CHANGES_REQUESTED.
+
+Final message: VERDICT, one line per finding status, one line per
+regression if any, report path.