Add Windows exe icon, clean release filenames, fix Linux build

- Embed microphone icon in Windows exe via winresource
- Rename release artifacts to friendly names (linux-x86_64, windows-x86_64)
- Fix warn macro import for Linux build
- Add cargo PATH to release script
- Fix tea CLI asset upload syntax

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

build.rs

@@ -0,0 +1,10 @@
+fn main() {
+    let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+    if target_os == "windows" {
+        let mut res = winresource::WindowsResource::new();
+        res.set_icon("assets/mouth.ico");
+        if let Err(e) = res.compile() {
+            eprintln!("cargo:warning=Failed to embed Windows icon: {e}");
+        }
+    }
+}