fix: suppress spurious --native warning when set via env var (#611)

* fix: suppress spurious --native warning when set via env var

When AGENT_BROWSER_NATIVE=1 is set via environment variable, every
command after the first would warn:

  ⚠ --native ignored: daemon already running.

This is a false positive — the daemon was already spawned in native
mode and inherited the env var. The warning should only fire when
--native is explicitly passed on the CLI to an already-running daemon.

Add cli_native flag (consistent with existing cli_* pattern) to
distinguish CLI origin from env var origin.

* fix: add flag to test cfg

* fix: cli_native should track flag presence, not value

--native false on CLI should still warn when daemon is already
running, since the user is explicitly trying to change the mode.

cli/src/main.rs

@@ -463,7 +463,7 @@ fn main() {
             flags.ignore_https_errors.then_some("--ignore-https-errors"),
             flags.cli_allow_file_access.then_some("--allow-file-access"),
             flags.cli_download_path.then_some("--download-path"),
-            flags.native.then_some("--native"),
+            flags.cli_native.then_some("--native"),
         ]
         .into_iter()
         .flatten()