feat: add debug clear-memories command to hard-wipe memories state (#13085)

#### what
adds a `codex debug clear-memories` command to help with clearing all
memories state from disk, sqlite db, and marking threads as
`memory_mode=disabled` so they don't get resummarized when the
`memories` feature is re-enabled.

#### tests
add tests

codex-rs/cli/src/main.rs

@@ -22,6 +22,8 @@ use codex_exec::Command as ExecCommand;
 use codex_exec::ReviewArgs;
 use codex_execpolicy::ExecPolicyCheckCommand;
 use codex_responses_api_proxy::Args as ResponsesApiProxyArgs;
+use codex_state::StateRuntime;
+use codex_state::state_db_path;
 use codex_tui::AppExitInfo;
 use codex_tui::Cli as TuiCli;
 use codex_tui::ExitReason;
@@ -163,6 +165,10 @@ struct DebugCommand {
 enum DebugSubcommand {
     /// Tooling: helps debug the app server.
     AppServer(DebugAppServerCommand),
+
+    /// Internal: reset local memory state for a fresh start.
+    #[clap(hide = true)]
+    ClearMemories,
 }
 
 #[derive(Debug, Parser)]
@@ -751,6 +757,9 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
             DebugSubcommand::AppServer(cmd) => {
                 run_debug_app_server_command(cmd)?;
             }
+            DebugSubcommand::ClearMemories => {
+                run_debug_clear_memories_command(&root_config_overrides, &interactive).await?;
+            }
         },
         Some(Subcommand::Execpolicy(ExecpolicyCommand { sub })) => match sub {
             ExecpolicySubcommand::Check(cmd) => run_execpolicycheck(cmd)?,
@@ -877,6 +886,60 @@ fn maybe_print_under_development_feature_warning(
     );
 }
 
+async fn run_debug_clear_memories_command(
+    root_config_overrides: &CliConfigOverrides,
+    interactive: &TuiCli,
+) -> anyhow::Result<()> {
+    let cli_kv_overrides = root_config_overrides
+        .parse_overrides()
+        .map_err(anyhow::Error::msg)?;
+    let overrides = ConfigOverrides {
+        config_profile: interactive.config_profile.clone(),
+        ..Default::default()
+    };
+    let config =
+        Config::load_with_cli_overrides_and_harness_overrides(cli_kv_overrides, overrides).await?;
+
+    let state_path = state_db_path(config.sqlite_home.as_path());
+    let mut cleared_state_db = false;
+    if tokio::fs::try_exists(&state_path).await? {
+        let state_db = StateRuntime::init(
+            config.sqlite_home.clone(),
+            config.model_provider_id.clone(),
+            None,
+        )
+        .await?;
+        state_db.reset_memory_data_for_fresh_start().await?;
+        cleared_state_db = true;
+    }
+
+    let memory_root = config.codex_home.join("memories");
+    let removed_memory_root = match tokio::fs::remove_dir_all(&memory_root).await {
+        Ok(()) => true,
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => false,
+        Err(err) => return Err(err.into()),
+    };
+
+    let mut message = if cleared_state_db {
+        format!("Cleared memory state from {}.", state_path.display())
+    } else {
+        format!("No state db found at {}.", state_path.display())
+    };
+
+    if removed_memory_root {
+        message.push_str(&format!(" Removed {}.", memory_root.display()));
+    } else {
+        message.push_str(&format!(
+            " No memory directory found at {}.",
+            memory_root.display()
+        ));
+    }
+
+    println!("{message}");
+
+    Ok(())
+}
+
 /// Prepend root-level overrides so they have lower precedence than
 /// CLI-specific ones specified after the subcommand (if any).
 fn prepend_config_flags(