docs: add missing Wave 2 Optimizer & Benchmarks entry

Wave 2 (PRs #249, #251, #253) was missing from CHANGELOG.md, ROADMAP.md,
and TEST_COVERAGE.md:

- CHANGELOG.md: add Wave 2 section between Wave 3 and Wave 1 entries
- ROADMAP.md: add Wave 2 to timeline between Wave 1 and Wave 3
- TEST_COVERAGE.md: add Wave 2 completion status note (no new tests —
  all optimizer + benchmark work covered by existing 850 tests)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: adityamukho

CHANGELOG.md

@@ -43,6 +43,34 @@ Six PRs hardening the v1.0.0 codebase: WAL fault injection, storage/migration re
 
 ---
 
+## Wave 2 Optimizer & Benchmarks — 2026-05-16
+
+### Summary
+
+Three optimisation PRs extending the Wave 1 performance work. No API changes, no file-format changes, no new runtime dependencies. Test count unchanged at 850.
+
+**PR #249 — #207 + #206: Predicate Push-Down & Mixed Rule Optimization**
+
+- `optimizer::plan()` extended to accept `Expr` (predicate/arithmetic) clauses; they are interleaved at the earliest position where all their variables are bound, minimising intermediate binding sets
+- `StratifiedEvaluator` gains mixed-rule path: when a rule stratum contains both positive-only rules and rules with `not`/`not-join`, the evaluator now evaluates all positive rules first and applies negation filters in a second pass within the same stratum — eliminates a class of ordering-dependent bugs in cross-stratum negation
+
+**PR #251 — #205: Cost-Based `not`/`or` Ordering**
+
+- `optimizer::plan()` assigns selectivity estimates to `not`/`not-join` and `or`/`or-join` clauses; they are sorted after their ground-variable producers but before unconstrained pattern scans
+- `not`/`not-join` blocks placed after the patterns that produce their join variables (was: end of plan regardless); `or`/`or-join` blocks placed by estimated output cardinality
+
+**PR #253 — #229: SIMD Benchmarking & Crossover Analysis**
+
+- `benches/simd_helpers.rs`: `valid_time_filter_simd`, `as_of_filter_simd`, `sum_simd_i64` — portable SIMD kernels using `wide::i64x4` / `u64x4`
+- Criterion benchmark groups: `simd_temporal`, `simd_as_of`, `simd_aggregate` — scalar vs. SIMD crossover analysis at 1K–1M facts
+- Analysis result: SIMD crossover occurs at ~8K–16K facts per query; scalar path preferred below that threshold; SIMD integration deferred to post-1.0 backlog pending real-workload profiling
+
+### Tests
+
+850 tests passing (844 passing + 6 ignored: confirmed `or`+neg-cycle stratification bug, deferred to post-1.0 backlog). All Wave 2 PRs are optimisations; no new integration tests added.
+
+---
+
 ## Wave 1 Performance — 2026-05-15
 
 ### Summary

ROADMAP.md

@@ -1662,6 +1662,7 @@ When evaluating features, ask:
 - ✅ Phase 8.3d: Complete (April 2026) — Node.js `minigraf` on npm, 795 tests
 - ✅ Phase 8: Complete (May 2026) — v1.0.0
 - ✅ Wave 1 Performance: Complete (May 2026) — hash-join cluster + selective B+Tree lookup (#202, #203, #204, #208), 850 tests
+- ✅ Wave 2 Optimizer & Benchmarks: Complete (May 2026) — predicate push-down (#207, #206), cost-based not/or ordering (#205), SIMD crossover analysis (#229), 850 tests
 - ✅ Wave 3 Reliability: Complete (May 2026) — WAL fault injection, migration matrix, index corruption resilience, property-based testing, coverage gates, long-haul smoke, XTDB/Datomic compat (#209, #210, #212, #213, #214, #215, #216, #217, #219, #220, #221), 935 tests
 - 🎯 Phase 9: Ongoing (Ecosystem — integration examples, cookbook, GraphRAG/LangChain examples)
 

TEST_COVERAGE.md

@@ -61,6 +61,14 @@
 
 ---
 
+## Wave 2 Optimizer & Benchmarks Completion Status: ✅ COMPLETE
+
+**Wave 2 issues**: #207 + #206 (predicate push-down + mixed rule optimization), #205 (cost-based not/or ordering), #229 (SIMD benchmarking + crossover analysis)
+
+No new integration tests added — Wave 2 is entirely optimizer and benchmark work. Existing 850 tests cover all affected code paths. New benchmark groups: `simd_temporal`, `simd_as_of`, `simd_aggregate`.
+
+---
+
 ## Wave 1 Performance Completion Status: ✅ COMPLETE
 
 **Wave 1 issues**: #208 (selective B+Tree lookup), #202 (not/not-join hash-join), #203 (or/or-join hash-join), #204 (join_with_pattern hash-join)