Simplify fix: use rm before echo + chmod

The pipe-based `echo | install /dev/stdin` approach doesn't work
reliably on macOS (piping to /dev/stdin fails on Darwin).

Simply removing the file first achieves the same result: rm succeeds
on files owned by other users (only needs directory write permission),
then echo + chmod work on the newly created file we own.

See: nix-community/nix-direnv#647 (comment)

Assisted-By: claude-opus-4-5-20251101 via Claude Code

Author: tennox

src/modules/tasks.nix

@@ -210,14 +210,12 @@ in
         description = "Runs when entering the shell";
         exec = ''
           mkdir -p "$DEVENV_DOTFILE" || { echo "Failed to create $DEVENV_DOTFILE"; exit 1; }
-
-          # Write to temp file first, then use install to atomically replace.
-          # This works even when the target is owned by another user (e.g., root),
-          # as install unlinks and recreates the file.
-          _tmp="$DEVENV_DOTFILE/load-exports.$$"
-          printf '%s\n' "$DEVENV_TASK_ENV" >"$_tmp"
-          install -m 755 "$_tmp" "$DEVENV_DOTFILE/load-exports"
-          rm -f "$_tmp"
+          # Remove first to handle case where file is owned by another user (e.g., root).
+          # chmod would fail on such files, but rm + recreate works as long as we have
+          # write permission on the directory.
+          rm -f "$DEVENV_DOTFILE/load-exports" 2>/dev/null || true
+          echo "$DEVENV_TASK_ENV" > "$DEVENV_DOTFILE/load-exports"
+          chmod +x "$DEVENV_DOTFILE/load-exports"
         '';
       };
       "devenv:enterTest" = {