Per-project GitHub account for the PR section

[bil0ak]

simply put, i have one mac, multiple github accounts. personal, work, others...
using a zsh shortcut i had it specify different gh auth settings to different folders.
works perfect in terminal, but in t3code for the pr list is uses the main gh account, never checks if that specific project has different gh creds or not.

BELOW IS AI STUFF. 👇

Title

Per-project GitHub account for the PR section

What I want

Let a project choose which GitHub account T3 Code uses when it talks to gh, so one
machine can hold a personal account and a work account and the PR section shows the right
identity for whichever project is open.

Today the PR section resolves one account for all of github.com. Anyone with two
accounts gets correct PRs for one of them and a wrong or signed-out view for the other.

How people already do this outside T3

gh scopes its whole identity to a config directory, so the usual setup is a per-folder
GH_CONFIG_DIR:

gh() {
  case "$PWD/" in
    "$HOME"/Developer/work/*) GH_CONFIG_DIR=~/.config/gh-work command gh "$@" ;;
    *)                        command gh "$@" ;;
  esac
}

That works in a terminal and has no effect on T3.

Why it has no effect (at 324ddda31)

Three things, in increasing order of work to fix:

1. GH_CONFIG_DIR never reaches the server on desktop.
   apps/desktop/src/shell/DesktopShellEnvironment.ts:69 copies only an allowlist of names
   out of the login shell (PATH, SSH_AUTH_SOCK, XDG_*, …), and GH_CONFIG_DIR isn't
   on it. Launching T3 from a terminal inherits it and works; launching from the Dock
   doesn't. Same machine, same account, two different answers.

2. gh is spawned directly, not through a shell.
   apps/server/src/sourceControl/GitHubCli.ts:328 runs gh with cwd set to the project
   root and no env, so it inherits the server's environment. A shell function or alias
   never runs, and the project's own directory can't influence which account answers.

3. Viewer identity is cached per host, not per project.
   apps/server/src/pullRequest/PullRequestService.ts:710 keys viewersByHost on the host
   string with a 10-minute TTL (:117). Even if gh answered differently per cwd, every
   github.com project would collapse into whichever viewer resolved first.

Suggested shape

VcsProcess already takes an env passthrough (apps/server/src/vcs/VcsProcess.ts:27),
so most of the plumbing exists:

• Give a project an optional GH_CONFIG_DIR (or a general env overlay) and thread it
  through GitHubCli.execute into the spawn.
• Key viewersByHost on (host, configDir). Without this, one project's identity is
  served to another out of the cache and the feature silently half-works.

Both together are what makes two accounts usable.

Smallest useful step

Adding GH_CONFIG_DIR to LOGIN_SHELL_ENV_NAMES fixes item 1 alone. That doesn't give
per-project accounts, but it does make a single non-default gh config work on desktop
instead of reporting a logged-in user as signed out — and it's a one-line change that can
land independently of the rest.

Environment

• T3 Code: 0.0.34-nightly.20260819.1130
• macOS Tahoe 26.5, desktop app
• gh installed via Homebrew