feat(weld): phase alignment for layered bass, release 0.1.0

Weld hears the other bass layer through the sidechain and fits polarity
plus up to four RBJ allpass sections to the measured cross-spectrum, so
the layers sum instead of cancelling. No latency; the layer on its own
keeps its sound.

- Worker thread: Welch cross-spectrum and coherence, Nelder-Mead fit with
  1/f weighting, a per-band loss penalty and model selection by share of
  the achievable gain; GCC-PHAT lag detection flags a late layer.
- Audio thread: allocation-free chain with a 40 ms warm-up and 40 ms
  crossfade per new fit; mono blocks go to the worker through a lock-free
  queue.
- Follow / Learn / Hold; the fit is persisted and restored without a
  crossfade.
- Editor: per-band loss and recovery against a perfect alignment, phase
  before and after, recovered dB, time offset and status.
- Tests for flat magnitude, crossfade, fit targets, Follow hysteresis,
  Learn, silence, realtime allocation and the persisted fit in the host.

plugins/weld/plugin/Cargo.lock

@@ -1074,12 +1074,39 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bf50223579dc7cdcfb3bfcacf7069ff68243f8c363f62ffa99cf000a6b9c451"
 
+[[package]]
+name = "num-complex"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73f88a1307638156682bada9d7604135552957b7818057dcef22705b4d509495"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-conv"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "521739c6d2bac4aa25192232afe6841231376b2b26d4d9fae5ecf8ca5772e441"
 
+[[package]]
+name = "num-integer"
+version = "0.1.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ce2d95d4b3734dc35aa2f45e1aa22cd416814592a4f9d9205e11affd5b8e10b"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "num_enum"
 version = "0.7.6"
@@ -1454,6 +1481,15 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a6394b9e965e73d0a289ee54f589087e2c676aedf60885baf52c76b771e4958"
 
+[[package]]
+name = "primal-check"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc0d895b311e3af9902528fbb8f928688abbd95872819320517cc24ca6b2bd08"
+dependencies = [
+ "num-integer",
+]
+
 [[package]]
 name = "proc-macro-crate"
 version = "3.5.0"
@@ -1547,6 +1583,20 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustfft"
+version = "6.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21db5f9893e91f41798c88680037dba611ca6674703c1a18601b01a72c8adb89"
+dependencies = [
+ "num-complex",
+ "num-integer",
+ "num-traits",
+ "primal-check",
+ "strength_reduce",
+ "transpose",
+]
+
 [[package]]
 name = "rustix"
 version = "0.38.44"
@@ -1695,6 +1745,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "strength_reduce"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe895eb47f22e2ddd4dabc02bce419d2e643c8e3b585c78158b349195bc24d82"
+
 [[package]]
 name = "syn"
 version = "1.0.109"
@@ -1864,6 +1920,16 @@ version = "0.1.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "db97caf9d906fbde555dd62fa95ddba9eecfd14cb388e4f491a66d74cd5fb79a"
 
+[[package]]
+name = "transpose"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ad61aed86bc3faea4300c7aee358b4c6d0c8d6ccc36524c96e4c92ccf26e77e"
+dependencies = [
+ "num-integer",
+ "strength_reduce",
+]
+
 [[package]]
 name = "ttf-parser"
 version = "0.25.1"
@@ -2005,6 +2071,8 @@ dependencies = [
 name = "weld-core"
 version = "0.1.0"
 dependencies = [
+ "crossbeam-queue",
+ "rustfft",
  "serde",
 ]