docs(compliance): regrade BP-3/SEP-2243/GAP-CF-9 rows; record 2026 integration-test release gate

On the independent production evidence committed in the prior slice:
- 207 (dialect validation) ❌→✅, 408 (x-mcp-header rejection) ❌→✅,
  538 (sampling message-shape) ❌→✅
- 212 (DoS bounds SHOULD) ➖→🟡 and 548 (validate message content SHOULD)
  ❌→🟡 — partially met; remaining behavior named in each row.
- Totals recomputed mechanically: 322✅ / 72🟡 / 9❌ / 12🧪 / 126➖ (541).

Records an explicit open release gate in the E2E test plan: the workspace
integration-tests crate is pinned to protocol-2025-11-25, so whole-workspace
cargo test does not exercise the 2026 lane — a 2026-pinned integration-test
target is required before release readiness. Row 718 left unchanged.

Author: hortovanyi