chore: remove the TypeScript code from the repository (#2048)

This deletes the bulk of the `codex-cli` folder and eliminates the logic
that builds the TypeScript code and bundles it into the release.

Since this PR modifies `.github/workflows/rust-release.yml`, to test
changes to the release process, I locally commented out all of the "is
this commit on upstream `main`" checks in
`scripts/create_github_release.sh` and ran:

```
./codex-rs/scripts/create_github_release.sh 0.20.0-alpha.4
```

Which kicked off:

https://github.com/openai/codex/actions/runs/16842085113

And the release artifacts appear legit!

https://github.com/openai/codex/releases/tag/rust-v0.20.0-alpha.4

codex-cli/scripts/stage_release.sh

@@ -9,9 +9,6 @@
 #   --tmp <dir>  : Use <dir> instead of a freshly created temp directory.
 #   -h|--help    : Print usage.
 #
-# NOTE: This script is intended to be run from the repository root via
-#       `pnpm --filter codex-cli stage-release ...` or inside codex-cli with the
-#       helper script entry in package.json (`pnpm stage-release ...`).
 # -----------------------------------------------------------------------------
 
 set -euo pipefail
@@ -94,15 +91,10 @@ pushd "$CODEX_CLI_ROOT" >/dev/null
 
 # 1. Build the JS artifacts ---------------------------------------------------
 
-pnpm install
-pnpm build
-
 # Paths inside the staged package
 mkdir -p "$TMPDIR/bin"
 
 cp -r bin/codex.js "$TMPDIR/bin/codex.js"
-cp -r dist "$TMPDIR/dist"
-cp -r src "$TMPDIR/src" # keep source for TS sourcemaps
 cp ../README.md "$TMPDIR" || true # README is one level up - ignore if missing
 
 # Modify package.json - bump version and optionally add the native directory to