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/commands.rs

@@ -2100,6 +2100,7 @@ mod tests {
             cli_allow_file_access: false,
             cli_annotate: false,
             cli_download_path: false,
+            cli_native: false,
             annotate: false,
             color_scheme: None,
             download_path: None,