Okay, this seems promising

.direnv/bin/nix-direnv-reload

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -e
+if [[ ! -d "/mnt/removable/Projects/Rust/floating-calculator" ]]; then
+  echo "Cannot find source directory; Did you move it?"
+  echo "(Looking for "/mnt/removable/Projects/Rust/floating-calculator")"
+  echo 'Cannot force reload with this script - use "direnv reload" manually and then try again'
+  exit 1
+fi
+
+# rebuild the cache forcefully
+_nix_direnv_force_reload=1 direnv exec "/mnt/removable/Projects/Rust/floating-calculator" true
+
+# Update the mtime for .envrc.
+# This will cause direnv to reload again - but without re-building.
+touch "/mnt/removable/Projects/Rust/floating-calculator/.envrc"
+
+# Also update the timestamp of whatever profile_rc we have.
+# This makes sure that we know we are up to date.
+touch -r "/mnt/removable/Projects/Rust/floating-calculator/.envrc" "/mnt/removable/Projects/Rust/floating-calculator/.direnv"/*.rc

.direnv/flake-inputs/30kd4b18byfkr392j9m875zhmn26b0lh-source

@@ -0,0 +1 @@
+/nix/store/30kd4b18byfkr392j9m875zhmn26b0lh-source

.direnv/flake-inputs/8s34lwa58kh7412r209gkvpsscql78hg-source

@@ -0,0 +1 @@
+/nix/store/8s34lwa58kh7412r209gkvpsscql78hg-source

.direnv/flake-inputs/dx2qikyb4dyb6hbdfywbmsyla0z5a1h3-source

@@ -0,0 +1 @@
+/nix/store/dx2qikyb4dyb6hbdfywbmsyla0z5a1h3-source

.direnv/flake-profile-a5d5b61aa8a61b7d9d765e1daf971a9a578f1cfa

@@ -0,0 +1 @@
+/nix/store/zw6zvmvd7w63wm8y562m4hjj2w3gixz4-nix-shell-env