refactor: extract ModeBitmap files (no contract change)

[Code0987]

Design

docs/design/2026-09-02-refactor-bitmap.md

Independent of #40 (HLL extract). Same layout, Bitmap only.

What landed

Same BitSet / BitGet / BitCount / BitPos contract.

File	Role
pkg/store/bitmap.go	store methods (out of memory.go)
pkg/engine/bitmap.go	public verbs
pkg/engine/bitmap_apply.go	owner write + inbox apply
pkg/engine/bitmap_cluster.go	forward / snapshot / GetOrLoad

Tests

go test ./pkg/bitmapx ./pkg/store ./pkg/engine

Local bench

BenchmarkStoreGetHit 2 allocs/op, BenchmarkEngineGetHit 15 allocs/op (flat).

Bench risk

No new Get/Peek logic. Shared smoke/micro ±10%. Get-hit allocs must stay flat.

[github-actions]

SuperCache bench vs main

Both sides ran once on this same GitHub runner (main, then this PR). Not a merge gate.

Baseline: 34679e7 (2026-09-02T13:44:13Z) → this run: 34679e7 (2026-09-02T13:42:58Z)

scbench smoke

cell	ops/s (main → PR)	Δ ops/s	p50	p99
get/hit n=1 c=1 uniform	8795 → 8805	+0.1%	113µs → 113µs	190µs → 196µs
get/hit n=1 c=10 uniform	34035 → 33595	-1.3%	267µs → 270µs	812µs → 828µs
get/hit n=3 c=10 uniform	39001 → 38051	-2.4%	224µs → 228µs	928µs → 975µs
miss/miss-cacheonly n=1 c=1 uniform	8707 → 8584	-1.4%	114µs → 115µs	214µs → 217µs
miss/miss-cacheonly n=1 c=10 uniform	36056 → 35880	-0.5%	252µs → 253µs	803µs → 801µs
set/put n=1 c=1 uniform	8601 → 8640	+0.4%	114µs → 114µs	210µs → 198µs
set/put n=1 c=10 uniform	32339 → 32818	+1.5%	279µs → 277µs	871µs → 830µs

Δ ops/s: green-ish is higher throughput. Latency: lower is better.

go test -bench (ns/op)

benchmark	ns/op (main → PR)	Δ	allocs/op
BenchmarkEngineBitCount	170 → 170	+0.5%	0 → 0
BenchmarkEngineBitGetHit	167 → 165	-1.4%	0 → 0
BenchmarkEngineBitGetHitParallel	215 → 206	-4.1%	0 → 0
BenchmarkEngineBitSet	505 → 504	-0.3%	2 → 2
BenchmarkEngineBitSetParallel	561 → 586	+4.5%	2 → 2
BenchmarkEngineCMSIncr	8209 → 9178	+11.8%	1 → 1
BenchmarkEngineCMSIncrN	8261 → 10961	+32.7% worse	1 → 1
BenchmarkEngineCMSIncrParallel	12204 → 15114	+23.8% worse	1 → 1
BenchmarkEngineCMSQueryHit	202 → 203	+0.5%	1 → 1
BenchmarkEngineCMSQueryHitParallel	249 → 252	+0.9%	1 → 1
BenchmarkEngineCounterGet	162 → 159	-1.8%	0 → 0
BenchmarkEngineCounterGetParallel	203 → 186	-8.3%	0 → 0
BenchmarkEngineDelete	769 → 772	+0.4%	6 → 6
BenchmarkEngineGeoAdd	9870 → 9930	+0.6%	8 → 8
BenchmarkEngineGeoCard	160 → 162	+1.3%	0 → 0
BenchmarkEngineGeoPosHit	108 → 102	-5.1%	0 → 0
BenchmarkEngineGeoRadius	350645 → 355585	+1.4%	1016 → 1016
BenchmarkEngineGetHit	1253 → 1284	+2.5%	15 → 15
BenchmarkEngineGetHitParallel	1248 → 1215	-2.6%	15 → 15
BenchmarkEngineGetMissCacheOnly	873 → 877	+0.4%	14 → 14
BenchmarkEngineGetMissCacheOnlyParallel	657 → 671	+2.1%	14 → 14
BenchmarkEngineGetMissLoadThrough	1616 → 1631	+0.9%	24 → 24
BenchmarkEngineGetMissLoadThroughParallel	1794 → 1880	+4.8%	23 → 23
BenchmarkEngineHGetAll	15137 → 15713	+3.8%	134 → 134
BenchmarkEngineHGetHit	108 → 109	+0.4%	1 → 1
BenchmarkEngineHGetHitParallel	138 → 136	-1.8%	1 → 1
BenchmarkEngineHGetMiss	174 → 179	+3.1%	0 → 0
BenchmarkEngineHLLAdd	2072 → 2770	+33.7% worse	1 → 1
BenchmarkEngineHLLAddParallel	2874 → 3560	+23.9% worse	1 → 1
BenchmarkEngineHLLCountHit	115689 → 116107	+0.4%	0 → 0
BenchmarkEngineHLLCountHitParallel	119676 → 162134	+35.5% worse	0 → 0
BenchmarkEngineHLen	160 → 163	+2.1%	0 → 0
BenchmarkEngineHSet	10921 → 10990	+0.6%	6 → 6
BenchmarkEngineHSetParallel	12047 → 12348	+2.5%	6 → 6
BenchmarkEngineIncr	382 → 381	-0.4%	1 → 1
BenchmarkEngineIncrParallel	462 → 425	-7.8%	1 → 1
BenchmarkEngineJsonGet	195 → 195	+0.4%	1 → 1
BenchmarkEngineJsonGetHit	416 → 432	+3.8%	5 → 5
BenchmarkEngineJsonGetHitParallel	467 → 496	+6.2%	5 → 5
BenchmarkEngineJsonSet	28473 → 29965	+5.2%	215 → 215
BenchmarkEngineJsonSetParallel	16582 → 19773	+19.2%	118 → 119
BenchmarkEngineLIndexHit	182 → 184	+1.2%	1 → 1
BenchmarkEngineLLen	159 → 159	+0.0%	0 → 0
BenchmarkEngineLPush	10214 → 10952	+7.2%	18 → 18
BenchmarkEngineLRange	446 → 465	+4.3%	11 → 11
BenchmarkEnginePut	1626 → 1600	-1.6%	18 → 18
BenchmarkEnginePutParallel	1401 → 1470	+4.9%	18 → 18
BenchmarkEngineSetAdd	9557 → 9508	-0.5%	4 → 4
BenchmarkEngineSetCard	165 → 165	+0.2%	0 → 0
BenchmarkEngineSetContainsHit	104 → 103	-0.2%	0 → 0
BenchmarkEngineSetContainsHitParallel	120 → 121	+1.5%	0 → 0
BenchmarkEngineSetContainsMiss	183 → 175	-4.5%	0 → 0
BenchmarkEngineSetMembers	5690 → 5818	+2.2%	66 → 66
BenchmarkEngineSetRemove	1013 → 1004	-0.9%	1 → 1
BenchmarkEngineTopKAdd	1468 → 1545	+5.2%	21 → 21
BenchmarkEngineTopKAddParallel	1772 → 1837	+3.7%	21 → 21
BenchmarkEngineTopKListHit	569 → 595	+4.6%	11 → 11
BenchmarkEngineTopKListHitParallel	649 → 690	+6.3%	11 → 11
BenchmarkEngineZAdd	10251 → 10221	-0.3%	8 → 8
BenchmarkEngineZCard	160 → 159	-0.6%	0 → 0
BenchmarkEngineZRange	194431 → 195112	+0.4%	1017 → 1017
BenchmarkEngineZRangeByScore	197413 → 199418	+1.0%	1021 → 1021
BenchmarkEngineZScoreHit	103 → 103	+0.4%	0 → 0
BenchmarkStoreBitSet	112 → 112	-0.2%	1 → 1
BenchmarkStoreCGetHit	72 → 72	-0.1%	0 → 0
BenchmarkStoreCIncr	101 → 101	+0.0%	1 → 1
BenchmarkStoreCMSIncr	120 → 121	+1.0%	0 → 0
BenchmarkStoreCMSIncrN	121 → 121	+0.0%	0 → 0
BenchmarkStoreGeoAdd	9543 → 9675	+1.4%	2 → 2
BenchmarkStoreGeoPosHit	88 → 88	-0.4%	0 → 0
BenchmarkStoreGeoPosMiss	87 → 88	+1.2%	0 → 0
BenchmarkStoreGetHit	294 → 293	-0.6%	2 → 2
BenchmarkStoreGetHitParallel	363 → 345	-4.9%	2 → 2
BenchmarkStoreHGetHit	92 → 95	+3.7%	1 → 1
BenchmarkStoreHGetMiss	85 → 85	+0.8%	0 → 0
BenchmarkStoreHLLAdd	102 → 101	-0.7%	0 → 0
BenchmarkStoreHSet	10589 → 10598	+0.1%	3 → 3
BenchmarkStoreJsonSet	26956 → 26585	-1.4%	207 → 207
BenchmarkStorePut	311 → 306	-1.8%	2 → 2
BenchmarkStorePutParallel	343 → 358	+4.5%	2 → 2
BenchmarkStoreSetAdd	9242 → 9236	-0.1%	2 → 2
BenchmarkStoreSetContainsHit	87 → 89	+1.7%	0 → 0
BenchmarkStoreSetContainsMiss	84 → 84	+0.1%	0 → 0
BenchmarkStoreTopKAdd	1013 → 991	-2.2%	20 → 20
BenchmarkStoreZAdd	9509 → 9514	+0.1%	2 → 2
BenchmarkStoreZScoreHit	89 → 88	-0.4%	0 → 0
BenchmarkStoreZScoreMiss	88 → 86	-2.3%	0 → 0

_{Posted by CI bench job. Not a merge gate.}

[Code0987]

Opened too early — you wanted to review first. Branch feat/refactor-bitmap kept.

[Code0987]

Closing — you asked to review locally, not commit/PR.