Remove Zed-specific code from core libraries

- Delete script/install-linux (referenced non-existent Zed build files)
- Delete crates/util/src/shell_env.rs (Zed --printenv functionality)
- Remove Zed API URL builders from http_client:
  - build_zed_api_url()
  - build_zed_cloud_url()
  - build_zed_cloud_url_with_query()
  - build_zed_llm_url()
- Remove Zed-specific functions from util:
  - prevent_root_execution()
  - get_shell_safe_zed_path()
  - get_zed_cli_path()
  - load_login_shell_environment()
  - load_shell_from_passwd()
- Clean up unused imports

script/install-linux

@@ -1,22 +0,0 @@
-#!/usr/bin/env bash
-
-set -euxo pipefail
-
-if [[ $# -gt 0 ]]; then
-  echo "
-  Usage: ${0##*/}
-  Builds and installs zed onto your system into ~/.local, making it available as ~/.local/bin/zed.
-
-  Before running this you should ensure you have all the build dependencies installed with `./script/linux`.
-  "
-  exit 1
-fi
-export ZED_CHANNEL=$(<crates/zed/RELEASE_CHANNEL)
-export ZED_UPDATE_EXPLANATION="You need to fetch and rebuild zed in $(pwd)"
-script/bundle-linux
-
-arch="$(uname -m)"
-commit=$(git rev-parse HEAD | cut -c 1-7)
-archive="zed-linux-${arch}.tar.gz"
-export ZED_BUNDLE_PATH="${CARGO_TARGET_DIR:-target}/release/${archive}"
-script/install.sh