fix(just): chsh to nix-managed zsh after nix-switch

zsh now lives in nix/common.nix instead of meta/base.txt. Removing the
pacman zsh package leaves /etc/passwd dangling at /usr/bin/zsh, so new
login terminals die with 'shell not found'.

Mirror the chsh logic from nix/bootstrap.sh (which only runs on the VM
during first-time provisioning) into the nix-switch recipe so every
`just sync` / `just init` re-asserts the login shell — and the
host gets the same treatment as the VM.

Idempotent: skips when the shell already matches, skips when
~/.nix-profile/bin/zsh is missing (pre-bootstrap state).

1 files changed, 14 insertions, 0 deletions

diff --git a/justfile b/justfile
index a1cb7b3..dec9200 100644
--- a/justfile
+++ b/justfile
@@ -42,6 +42,20 @@ nix-switch:
     nix --extra-experimental-features 'nix-command flakes' \
         run home-manager/master -- \
         switch --impure --flake "{{ justfile_directory() }}/nix#${profile}" -b backup
+    # Ensure login shell points at the home-manager-managed zsh. Without
+    # this, removing zsh from meta/base.txt (now provisioned via nix)
+    # leaves /etc/passwd dangling at /usr/bin/zsh and new terminals die.
+    # Idempotent: only acts when current login shell differs.
+    NIX_ZSH="$HOME/.nix-profile/bin/zsh"
+    if [ -x "$NIX_ZSH" ]; then
+        if ! grep -qxF "$NIX_ZSH" /etc/shells 2>/dev/null; then
+            echo "$NIX_ZSH" | sudo tee -a /etc/shells >/dev/null
+        fi
+        current_shell="$(getent passwd "$USER" | cut -d: -f7)"
+        if [ "$current_shell" != "$NIX_ZSH" ]; then
+            sudo chsh -s "$NIX_ZSH" "$USER"
+        fi
+    fi
 
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