moved src-rust into a separate Rust source set; fixed binding generation

interop-panama/build.gradle.kts

···
     id("java")
 }
 
-val rustProjectDir = rootProject.layout.projectDirectory.dir("src-rust")
+val rustSources = objects.sourceDirectorySet("rust", "Rust sources").apply {
+    srcDir("src/main/rust")
+    include("**/*.rs", "Cargo.toml", "Cargo.lock")
+}
+
+val rustProjectDir = layout.projectDirectory.dir("src/main/rust")
 val rustTargetDir = rustProjectDir.dir("target/debug")
 val rustHeadersDir = rustProjectDir.dir("bindings")
 val jextractOutputDir = layout.buildDirectory.dir("generated/jextract")
···
     description = "Build src-rust cdylib with Cargo"
     workingDir = rustProjectDir.asFile
     commandLine("cargo", "build")
+    inputs.files(rustSources)
+    outputs.dir(layout.projectDirectory.dir("src/main/rust/target"))
 }
 
 val copyRustLib by tasks.registering(Copy::class) {
···
     dependsOn(buildRustCdylib)
     from(rustTargetDir.file(rustLibFileName))
     into(layout.buildDirectory.dir("native"))
+    inputs.dir(rustTargetDir)
+    outputs.dir(layout.buildDirectory.dir("native"))
 }
 
 val copyHeaders by tasks.registering(Copy::class) {
···
     dependsOn(buildRustCdylib)
     from(rustHeadersDir.file("jvm_interop.h"))
     into(layout.buildDirectory.dir("native"))
+    inputs.dir(rustHeadersDir)
+    outputs.dir(layout.buildDirectory.dir("native"))
 }
 
 // HACK: I'd rather interact with jextract as a build-time dependency, much like
···
     dependsOn(copyRustLib, copyHeaders)
     val nativeDir = layout.buildDirectory.dir("native").get().asFile
     val nativeLibPath = layout.buildDirectory.dir("native").get().file(rustLibFileName).get().asFile.absolutePath
+    inputs.dir(nativeDir)
     outputs.dir(jextractOutputDir)
     commandLine(
         "jextract",

src-rust/target/.rustc_info.json

···
-{"rustc_fingerprint":7833272153447333061,"outputs":{"17747080675513052775":{"success":true,"status":"","code":0,"stdout":"rustc 1.93.0 (254b59607 2026-01-19)\nbinary: rustc\ncommit-hash: 254b59607d4417e9dffbc307138ae5c86280fe4c\ncommit-date: 2026-01-19\nhost: x86_64-unknown-linux-gnu\nrelease: 1.93.0\nLLVM version: 21.1.8\n","stderr":""},"7971740275564407648":{"success":true,"status":"","code":0,"stdout":"___\nlib___.rlib\nlib___.so\nlib___.so\nlib___.a\nlib___.so\n/nix/store/2w8pppicnsddp3n61ar96cnv3r6iyrdh-rust-mixed\noff\npacked\nunpacked\n___\ndebug_assertions\npanic=\"unwind\"\nproc_macro\ntarget_abi=\"\"\ntarget_arch=\"x86_64\"\ntarget_endian=\"little\"\ntarget_env=\"gnu\"\ntarget_family=\"unix\"\ntarget_feature=\"fxsr\"\ntarget_feature=\"sse\"\ntarget_feature=\"sse2\"\ntarget_has_atomic=\"16\"\ntarget_has_atomic=\"32\"\ntarget_has_atomic=\"64\"\ntarget_has_atomic=\"8\"\ntarget_has_atomic=\"ptr\"\ntarget_os=\"linux\"\ntarget_pointer_width=\"64\"\ntarget_vendor=\"unknown\"\nunix\n","stderr":""},"11857020428658561806":{"success":true,"status":"","code":0,"stdout":"___\nlib___.rlib\nlib___.so\nlib___.so\nlib___.a\nlib___.so\n/nix/store/2w8pppicnsddp3n61ar96cnv3r6iyrdh-rust-mixed\noff\npacked\nunpacked\n___\ndebug_assertions\nemscripten_wasm_eh\nfmt_debug=\"full\"\noverflow_checks\npanic=\"unwind\"\nproc_macro\nrelocation_model=\"pic\"\ntarget_abi=\"\"\ntarget_arch=\"x86_64\"\ntarget_endian=\"little\"\ntarget_env=\"gnu\"\ntarget_family=\"unix\"\ntarget_feature=\"fxsr\"\ntarget_feature=\"sse\"\ntarget_feature=\"sse2\"\ntarget_feature=\"x87\"\ntarget_has_atomic\ntarget_has_atomic=\"16\"\ntarget_has_atomic=\"32\"\ntarget_has_atomic=\"64\"\ntarget_has_atomic=\"8\"\ntarget_has_atomic=\"ptr\"\ntarget_has_atomic_equal_alignment=\"16\"\ntarget_has_atomic_equal_alignment=\"32\"\ntarget_has_atomic_equal_alignment=\"64\"\ntarget_has_atomic_equal_alignment=\"8\"\ntarget_has_atomic_equal_alignment=\"ptr\"\ntarget_has_atomic_load_store\ntarget_has_atomic_load_store=\"16\"\ntarget_has_atomic_load_store=\"32\"\ntarget_has_atomic_load_store=\"64\"\ntarget_has_atomic_load_store=\"8\"\ntarget_has_atomic_load_store=\"ptr\"\ntarget_has_reliable_f128\ntarget_has_reliable_f16\ntarget_has_reliable_f16_math\ntarget_os=\"linux\"\ntarget_pointer_width=\"64\"\ntarget_thread_local\ntarget_vendor=\"unknown\"\nub_checks\nunix\n","stderr":""}},"successes":{}}

src-rust/target/CACHEDIR.TAG

···
-Signature: 8a477f597d28d172789f06886806bc55
-# This file is a cache directory tag created by cargo.
-# For information about cache directory tags see https://bford.info/cachedir/