## Summary
Fixes#355 — replaces O(n²) observation dedup in `Load()`,
`IngestNewFromDB()`, and `IngestNewObservations()` with an O(1)
map-based lookup.
## Changes
- Added `obsKeys map[string]bool` field to `StoreTx` for O(1) dedup
keyed on `observerID + "|" + pathJSON`
- Replaced all 3 linear-scan dedup sites in `store.go` with map lookups
- Lazy-init `obsKeys` for transmissions created before this change (in
`IngestNewFromDB` and `IngestNewObservations`)
- Added regression test (`TestObsDedupCorrectness`) verifying dedup
correctness
- Added nil-map safety test (`TestObsDedupNilMapSafety`)
- Added benchmark comparing map vs linear scan
## Benchmark Results (ARM64, 16 cores)
| Observations | Map (O(1)) | Linear (O(n)) | Speedup |
|---|---|---|---|
| 10 | 34 ns/op | 41 ns/op | 1.2x |
| 50 | 34 ns/op | 186 ns/op | 5.5x |
| 100 | 34 ns/op | 361 ns/op | 10.6x |
| 500 | 34 ns/op | 4,903 ns/op | **146x** |
Map lookup is constant time regardless of observation count. The linear
scan degrades quadratically — at 500 observations per transmission
(realistic for popular packets seen by many observers), the old code is
146x slower per dedup check.
All existing tests pass.
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Co-authored-by: you <you@example.com>
Kpa-clawbot