feat(M3): Clusterer trait + NME-SC for v1.0

CHANGELOG.md

@@ -53,6 +53,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - New manifest entry `[models.cam_pp_fp32]`. Profiles still resolve to
   `wespeaker_resnet34` until M6 swaps them.
 
+### Added (M3 — Clusterer trait + NME-SC)
+- `polyvoice::clusterer` module: `Clusterer` trait, `ClustererError`,
+  `AhcClusterer` (wraps legacy `agglomerative_cluster_auto`), `NmeScClusterer`
+  (NME-SC with eigengap auto-K, gated `spectral`+`clusterer`).
+- New Cargo feature `clusterer` (in default features). The AHC adapter is
+  wasm32-clean; NME-SC additionally requires the `spectral` feature.
+- Integration test on synthetic 4-cluster data (no model required) — runs in
+  every PR's normal `cargo test` (not `--ignored`).
+
 ## [0.5.2] - 2025-05-05
 
 ### Added

Cargo.toml

@@ -12,7 +12,7 @@ categories = ["multimedia::audio", "science"]
 crate-type = ["cdylib", "rlib"]
 
 [features]
-default = ["spectral", "segmentation", "embedder"]
+default = ["spectral", "segmentation", "embedder", "clusterer"]
 # ONNX-based embedding extractors (pulls ort).
 onnx = ["dep:ort"]
 # C FFI bindings.
@@ -41,6 +41,11 @@ segmentation = []
 # `ResNet34Adapter` additionally require `onnx`.
 embedder = []
 
+# v1.0 Clusterer trait + NME-SC + AHC adapters.
+# AHC adapter is wasm32-clean. NME-SC additionally requires `spectral` (which
+# pulls `faer`).
+clusterer = []
+
 # Model profile bundles. M0 only emits metadata; CLI uses these to pick which
 # manifest entries to ensure(). M5 will introduce INT8 model variants.
 profile-mobile = []