fix(bird_x): pass .env credentials to Node subprocesses for WSL2/headless auth

* chore: fix YAML error in argument-hint

* add codex auth support to responses API

* Use gpt-5.1-codex-mini as default model for Codex auth

Add CODEX_FALLBACK_MODELS chain (gpt-5.1-codex-mini → gpt-5.2) for
Codex endpoint which doesn't support standard OpenAI models like
gpt-4o-mini. Adds model fallback retry on 400 errors in the Codex
search path. Also adds test_codex_auth.py with 22 unit tests covering
JWT decoding, auth resolution, SSE parsing, and payload building.

* Pass .env credentials to Bird Node subprocesses for X auth

On platforms without browser cookie access (e.g. WSL2), Bird's
vendored Node.js module cannot read AUTH_TOKEN/CT0 from Firefox
or Chrome cookie stores. The .env config file already supports
these values, but they were only loaded into the Python config
dict — never exported to the environment of Node subprocesses.

- Add AUTH_TOKEN/CT0 to env.py config key loading
- Add set_credentials()/\_subprocess_env() to bird_x.py to inject
  credentials into the env dict passed to subprocess.run/Popen
- Call set_credentials() in main() before Bird auth detection

---------

Co-authored-by: Justin Williams <jblwilliams@gmail.com>

scripts/lib/ui.py

@@ -1,6 +1,5 @@
 """Terminal UI utilities for last30days skill."""
 
-import os
 import sys
 import time
 import threading
@@ -117,7 +116,7 @@ I just researched that for you. Here's what I've got right now:
 
 {status_line}
 
-You can unlock more sources with API keys — just ask me how and I'll walk you through it. More sources means better research, but it works fine as-is.
+You can unlock more sources with API keys or by signing in to Codex — just ask me how and I'll walk you through it. More sources means better research, but it works fine as-is.
 
 Some examples of what you can do:
 - "last30 what are people saying about Figma"
@@ -131,7 +130,7 @@ Just start with "last30" and talk to me like normal.
 
 # Shorter promo for single missing key
 PROMO_SINGLE_KEY = {
-    "reddit": "\n💡 You can unlock Reddit with an OpenAI API key — just ask me how.\n",
+    "reddit": "\n💡 You can unlock Reddit with an OpenAI API key or by running `codex login` — just ask me how.\n",
     "x": "\n💡 You can unlock X with an xAI API key — just ask me how.\n",
 }