feat: add layered --profile-v2 config files (#17141)

## Why

`--profile-v2 <name>` gives launchers and runtime entry points a named
profile config without making each profile duplicate the base user
config. The base `$CODEX_HOME/config.toml` still loads first, then
`$CODEX_HOME/<name>.config.toml` layers above it and becomes the active
writable user config for that session.

That keeps shared defaults, plugin/MCP setup, and managed/user
constraints in one place while letting a named profile override only the
pieces that need to differ.

## What Changed

- Added the shared `--profile-v2 <name>` runtime option with validated
plain names, now represented by `ProfileV2Name`.
- Extended config layer state so the base user config and selected
profile config are both `User` layers; APIs expose the active user layer
and merged effective user config.
- Threaded profile selection through runtime entry points: `codex`,
`codex exec`, `codex review`, `codex resume`, `codex fork`, and `codex
debug prompt-input`.
- Made user-facing config writes go to the selected profile file when
active, including TUI/settings persistence, app-server config writes,
and MCP/app tool approval persistence.
- Made plugin, marketplace, MCP, hooks, and config reload paths read
from the merged user config so base and profile layers both participate.
- Updated app-server config layer schemas to mark profile-backed user
layers.

## Limits

`--profile-v2` is still rejected for config-management subcommands such
as feature, MCP, and marketplace edits. Those paths remain tied to the
base `config.toml` until they have explicit profile-selection semantics.

Some adjacent background writes may still update base or global state
rather than the selected profile:

- marketplace auto-upgrade metadata
- automatic MCP dependency installs from skills
- remote plugin sync or uninstall config edits
- personality migration marker/default writes

## Verification

Added targeted coverage for profile name validation, layer
ordering/merging, selected-profile writes, app-server config writes,
session hot reload, plugin config merging, hooks/config fixture updates,
and MCP/app approval persistence.

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/utils/cli/src/lib.rs

@@ -5,6 +5,7 @@ mod sandbox_mode_cli_arg;
 mod shared_options;
 
 pub use approval_mode_cli_arg::ApprovalModeCliArg;
+pub use codex_protocol::config_types::ProfileV2Name;
 pub use config_override::CliConfigOverrides;
 pub use format_env_display::format_env_display;
 pub use sandbox_mode_cli_arg::SandboxModeCliArg;

codex-rs/utils/cli/src/shared_options.rs

@@ -2,6 +2,7 @@
 
 use crate::SandboxModeCliArg;
 use clap::Args;
+use codex_protocol::config_types::ProfileV2Name;
 use std::path::PathBuf;
 
 #[derive(Args, Debug, Default)]
@@ -33,6 +34,10 @@ pub struct SharedCliOptions {
     #[arg(long = "profile", short = 'p')]
     pub config_profile: Option<String>,
 
+    /// Layer $CODEX_HOME/<name>.config.toml on top of the base user config.
+    #[arg(long = "profile-v2")]
+    pub config_profile_v2: Option<ProfileV2Name>,
+
     /// Select the sandbox policy to use when executing model-generated shell
     /// commands.
     #[arg(long = "sandbox", short = 's')]
@@ -71,6 +76,7 @@ impl SharedCliOptions {
             oss,
             oss_provider,
             config_profile,
+            config_profile_v2,
             sandbox_mode,
             dangerously_bypass_approvals_and_sandbox,
             bypass_hook_trust,
@@ -83,6 +89,7 @@ impl SharedCliOptions {
             oss: root_oss,
             oss_provider: root_oss_provider,
             config_profile: root_config_profile,
+            config_profile_v2: root_config_profile_v2,
             sandbox_mode: root_sandbox_mode,
             dangerously_bypass_approvals_and_sandbox: root_dangerously_bypass_approvals_and_sandbox,
             bypass_hook_trust: root_bypass_hook_trust,
@@ -102,6 +109,9 @@ impl SharedCliOptions {
         if config_profile.is_none() {
             config_profile.clone_from(root_config_profile);
         }
+        if config_profile_v2.is_none() {
+            config_profile_v2.clone_from(root_config_profile_v2);
+        }
         if sandbox_mode.is_none() {
             *sandbox_mode = *root_sandbox_mode;
         }
@@ -136,6 +146,7 @@ impl SharedCliOptions {
             oss,
             oss_provider,
             config_profile,
+            config_profile_v2,
             sandbox_mode,
             dangerously_bypass_approvals_and_sandbox,
             bypass_hook_trust,
@@ -155,6 +166,9 @@ impl SharedCliOptions {
         if let Some(config_profile) = config_profile {
             self.config_profile = Some(config_profile);
         }
+        if let Some(config_profile_v2) = config_profile_v2 {
+            self.config_profile_v2 = Some(config_profile_v2);
+        }
         if subcommand_selected_sandbox_mode {
             self.sandbox_mode = sandbox_mode;
             self.dangerously_bypass_approvals_and_sandbox =