auth: CLI auth manager + `panto auth` subcommands

Add src/auth_manager.zig (turn-time resolution: load→login→refresh→exchange→
build credential, patch live config) and `panto auth status|login|logout`
subcommands with a line-based device-code presenter. Add config_file.loadFromString.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/main.zig b/src/main.zig
index e867c0e..dc611b4 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -11,6 +11,7 @@ const subcommand = @import("subcommand.zig");
 const session_paths = @import("session_paths.zig");
 const models_toml = @import("models_toml.zig");
 const config_file = @import("config_file.zig");
+const auth_manager = @import("auth_manager.zig");
 const glob = @import("glob.zig");
 const system_prompt = @import("system_prompt.zig");
 const command = @import("command.zig");
@@ -54,6 +55,7 @@ test {
     _ = subcommand;
     _ = models_toml;
     _ = config_file;
+    _ = auth_manager;
     _ = glob;
     _ = system_prompt;
     _ = command;