cli: rename profile v2 flag to --profile (#23883)

## Why

Profile v2 is taking over the user-facing profile selection path, so the
CLI no longer needs to expose the transitional `--profile-v2` spelling.
This switches the public args surface to `--profile` before the
remaining legacy profile plumbing is removed separately.

## What

- Rebind `--profile` and `-p` to the v2 profile name argument that
selects `$CODEX_HOME/<name>.config.toml`.
- Stop parsing the legacy shared CLI profile argument while keeping its
implementation path in place for follow-up cleanup.
- Update CLI validation, profile-name parse errors, and the
legacy-profile collision message/tests to refer to `--profile`.

## Testing

- `cargo test -p codex-cli -p codex-config -p codex-protocol -p
codex-utils-cli`

codex-rs/cli/src/main.rs

@@ -1477,7 +1477,7 @@ fn profile_v2_for_subcommand<'a>(
             subcommand: DebugSubcommand::PromptInput(_),
         }) => Ok(Some(profile_v2)),
         _ => anyhow::bail!(
-            "--profile-v2 only applies to runtime commands: `codex`, `codex exec`, `codex review`, `codex resume`, `codex fork`, and `codex debug prompt-input`."
+            "--profile only applies to runtime commands: `codex`, `codex exec`, `codex review`, `codex resume`, `codex fork`, and `codex debug prompt-input`."
         ),
     }
 }
@@ -2286,21 +2286,19 @@ mod tests {
 
     #[test]
     fn profile_v2_is_rejected_for_config_management_subcommands() {
-        assert!(
-            profile_v2_for_args(&["codex", "--profile-v2", "work", "features", "list"]).is_err()
-        );
+        assert!(profile_v2_for_args(&["codex", "--profile", "work", "features", "list"]).is_err());
     }
 
     #[test]
     fn profile_v2_is_allowed_for_runtime_subcommands() {
         assert_eq!(
-            profile_v2_for_args(&["codex", "--profile-v2", "work", "resume"])
+            profile_v2_for_args(&["codex", "--profile", "work", "resume"])
                 .expect("resume supports profile-v2")
                 .as_deref(),
             Some("work")
         );
         assert_eq!(
-            profile_v2_for_args(&["codex", "--profile-v2", "work", "debug", "prompt-input"])
+            profile_v2_for_args(&["codex", "--profile", "work", "debug", "prompt-input"])
                 .expect("debug prompt-input supports profile-v2")
                 .as_deref(),
             Some("work")
@@ -2310,8 +2308,7 @@ mod tests {
     #[test]
     fn profile_v2_rejects_non_plain_names_at_parse_time() {
         assert!(
-            MultitoolCli::try_parse_from(["codex", "--profile-v2", "nested/work", "resume"])
-                .is_err()
+            MultitoolCli::try_parse_from(["codex", "--profile", "nested/work", "resume"]).is_err()
         );
     }
 
@@ -2762,8 +2759,6 @@ mod tests {
                 "-m",
                 "gpt-5.1-test",
                 "-p",
-                "my-profile",
-                "--profile-v2",
                 "my-config",
                 "-C",
                 "/tmp",
@@ -2776,7 +2771,7 @@ mod tests {
 
         assert_eq!(interactive.model.as_deref(), Some("gpt-5.1-test"));
         assert!(interactive.oss);
-        assert_eq!(interactive.config_profile.as_deref(), Some("my-profile"));
+        assert_eq!(interactive.config_profile.as_deref(), None);
         assert_eq!(interactive.config_profile_v2.as_deref(), Some("my-config"));
         assert_matches!(
             interactive.sandbox_mode,