Replace crossbeam channel with std::sync::mpsc (#861)

* Replace crossbeam channel with std::sync::mpsc

- Replace all uses of crossbeam::channel with std::sync::mpsc
- Remove crossbeam dependency from all Cargo.toml files
- Update documentation to remove crossbeam references
- Use std::sync::mpsc::channel() instead of crossbeam::channel::unbounded()

Fixes #828

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* Update mod.rs

---------

Co-authored-by: Claude <noreply@anthropic.com>

crates/rapier2d-f64/Cargo.toml

@@ -73,7 +73,6 @@ parry2d-f64 = "0.22.0-beta.1"
 simba = "0.9"
 approx = "0.5"
 rayon = { version = "1", optional = true }
-crossbeam = "0.8"
 arrayvec = "0.7"
 bit-vec = "0.8"
 rustc-hash = "2"

crates/rapier2d/Cargo.toml

@@ -74,7 +74,6 @@ parry2d = "0.22.0-beta.1"
 simba = "0.9"
 approx = "0.5"
 rayon = { version = "1", optional = true }
-crossbeam = "0.8"
 arrayvec = "0.7"
 bit-vec = "0.8"
 rustc-hash = "2"

crates/rapier3d-f64/Cargo.toml

@@ -76,7 +76,6 @@ parry3d-f64 = "0.22.0-beta.1"
 simba = "0.9"
 approx = "0.5"
 rayon = { version = "1", optional = true }
-crossbeam = "0.8"
 arrayvec = "0.7"
 bit-vec = "0.8"
 rustc-hash = "2"

crates/rapier3d/Cargo.toml

@@ -78,7 +78,6 @@ parry3d = "0.22.0-beta.1"
 simba = "0.9"
 approx = "0.5"
 rayon = { version = "1", optional = true }
-crossbeam = "0.8"
 arrayvec = "0.7"
 bit-vec = "0.8"
 rustc-hash = "2"

crates/rapier_testbed2d-f64/Cargo.toml

@@ -50,7 +50,6 @@ web-time = { version = "1.1" }
 bitflags = "2"
 num_cpus = { version = "1", optional = true }
 wrapped2d = { version = "0.4", optional = true }
-crossbeam = "0.8"
 bincode = "1"
 Inflector = "0.11"
 md5 = "0.7"

crates/rapier_testbed2d/Cargo.toml

@@ -50,7 +50,6 @@ web-time = { version = "1.1" }
 bitflags = "2"
 num_cpus = { version = "1", optional = true }
 wrapped2d = { version = "0.4", optional = true }
-crossbeam = "0.8"
 bincode = "1"
 Inflector = "0.11"
 md5 = "0.7"

crates/rapier_testbed3d-f64/Cargo.toml

@@ -51,7 +51,6 @@ rand_pcg = "0.3"
 web-time = { version = "1.1" }
 bitflags = "2"
 num_cpus = { version = "1", optional = true }
-crossbeam = "0.8"
 bincode = "1"
 md5 = "0.7"
 Inflector = "0.11"

crates/rapier_testbed3d/Cargo.toml

@@ -52,7 +52,6 @@ glam = { version = "0.27", optional = true } # For Physx
 num_cpus = { version = "1", optional = true }
 physx = { version = "0.19", features = ["glam"], optional = true }
 physx-sys = { version = "0.11", optional = true }
-crossbeam = "0.8"
 bincode = "1"
 md5 = "0.7"
 Inflector = "0.11"