Fix CPU reporting: Android support, TCP remote CPU parsing

- Add target_os = "android" to CPU sampler (reads /proc/stat like Linux)
- Parse remote CPU from interleaved TCP status messages in BOTH mode
- Add dedicated status reader for TX-only mode (reads server's 12-byte
  status messages to get remote CPU and enable speed adaptation)
- Add 3 CPU integration tests: local CPU, TCP BOTH remote, TCP TX-only

Fixes: Android always showing cpu: 0%/0%, TCP remote CPU always 0%
on all platforms (btest-to-btest and btest-to-MikroTik).

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

src/cpu.rs

@@ -29,7 +29,7 @@ pub fn get() -> u8 {
 
 // --- Platform-specific implementation ---
 
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "android"))]
 fn get_cpu_times() -> (u64, u64) {
     // Read /proc/stat: cpu  user nice system idle iowait irq softirq steal
     if let Ok(content) = std::fs::read_to_string("/proc/stat") {
@@ -165,6 +165,7 @@ fn get_cpu_times() -> (u64, u64) {
 
 #[cfg(not(any(
     target_os = "linux",
+    target_os = "android",
     target_os = "macos",
     target_os = "windows",
     target_os = "freebsd",
@@ -193,6 +194,7 @@ mod tests {
         // On supported platforms, total should be > 0
         if cfg!(any(
             target_os = "linux",
+            target_os = "android",
             target_os = "macos",
             target_os = "windows",
             target_os = "freebsd",