fix nested config items in codex app

[lilly-luo]

#473 was a previous attempt to fix codex app in ucode. i tested by running uv run ucode codex app and it worked. however, when i installed a new ucode and ran ucode codex app, it failed with the error below.

this is because when i tested previously, uv run uses the uv.lock where as a freshly installed ucode does not respect uv.lock. we specify tomlkit>=0.13.0. the uv.lock has 0.14 pinned which works but a freshly installed ucode has tomlkit 0.15.1 which is not compatible with this change.

i've since updated the uv.lock #496 so that uv run will be consistent with future installs so we don't have this discrepancy in the future. this PR makes a fix such that ucode codex app will actually work

before:

➜  ucode git:(lilly/fix-codex-app-again) ucode codex app

╭────────────────────────────────────╮
│ Launching Codex with Unity Gateway │
╰────────────────────────────────────╯
✔ Starting Codex
╭────────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────────────────────────────────╮
│ /Users/lilly.luo/.local/share/uv/tools/ucode/lib/python3.12/site-packages/ucode/cli.py:2402 in codex_cmd                                       │
│                                                                                                                                                │
│   2399 │   │   print_success("Codex smart routing disabled; ucode routing hooks removed")                                                      │
.......
ValueError: Inline tables cannot contain a table

after (with the updated uv.lock):

➜  ucode git:(lilly/fix-codex-app-again) uv run codex app 
Opening Codex Desktop at /Applications/Codex.app...
Opening workspace /Users/lilly.luo/ucode...

[lilly-luo]

this will be fixed here: #502