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/flags.rs

@@ -250,6 +250,7 @@ pub struct Flags {
     pub cli_allow_file_access: bool,
     pub cli_annotate: bool,
     pub cli_download_path: bool,
+    pub cli_native: bool,
 }
 
 pub fn parse_flags(args: &[String]) -> Flags {
@@ -352,6 +353,7 @@ pub fn parse_flags(args: &[String]) -> Flags {
         cli_allow_file_access: false,
         cli_annotate: false,
         cli_download_path: false,
+        cli_native: false,
     };
 
     let mut i = 0;
@@ -568,6 +570,7 @@ pub fn parse_flags(args: &[String]) -> Flags {
             "--native" => {
                 let (val, consumed) = parse_bool_arg(args, i);
                 flags.native = val;
+                flags.cli_native = true;
                 if consumed {
                     i += 1;
                 }