fix(install): cross-platform binary install + PATH conflict detection

install_binary() now:
1. Automatically picks best location per platform:
   - macOS: ~/.cargo/bin/ (no sudo, in PATH for Rust users)
   - Linux: ~/.cargo/bin/ → /usr/local/bin → ~/.local/bin/
   - Windows: /usr/local/bin (Git Bash/MSYS2)
2. Detects if old binary exists at a different PATH location
   and warns the user: 'There is ANOTHER gyandoot at ...'
3. Verifies 'command -v gyandoot' resolves correctly after install
4. Shows shell profile instructions if PATH needs updating

Previous issue: always installed to /usr/local/bin with sudo,
overwriting the old binary from install.sh but not warning if
another copy existed elsewhere in PATH.

crates/gyandoot-agent/src/browser_manager.rs

@@ -408,7 +408,7 @@ async fn trigger_daemon_start(npx: &str, session: &str) -> Result<(), String> {
 
 /// Find the daemon.js entrypoint in the globally installed camoufox-browser package.
 /// Tries: npm root -g → find dist/daemon.js
-async fn find_daemon_js(npx: &str) -> Result<std::path::PathBuf, String> {
+async fn find_daemon_js(_npx: &str) -> Result<std::path::PathBuf, String> {
     // Try `npm root -g` to find global node_modules
     let root_output = Command::new("npm")
         .args(&["root", "-g"])