fix: improve shell detection, curl flags, and cleanup robustness

- Use ZSH_VERSION instead of ZSH_NAME for reliable zsh detection
- Document NVIM_* env vars as optional external overrides
- Add -fsSL flags to curl for mise bootstrap
- Consolidate duplicate shellcheck directives in install-fonts.sh
- Add explicit return 0 to cleanup script helper functions
- Add actionable remediation to uv-not-found error message

scripts/install-python-packages.sh

@@ -9,7 +9,7 @@ msgr run "Starting to install Python libraries"
 
 # Ensure uv is available
 if ! command -v uv &> /dev/null; then
-  msgr err "uv not found — install it via mise first"
+  msgr err "uv not found — install it via mise first (run: dfm install mise)"
   exit 1
 fi