[Fix] Reject bare LTS codenames in nvm install

Previously, `nvm install Argon` would succeed by matching the LTS name
in the version description (e.g., "v4.9.1 (Latest LTS: Argon)"), but
`nvm uninstall Argon` would fail because "Argon" is not a valid alias or not a valid version.

Changes:
- Added pattern matching check in nvm_remote_version (nvm.sh:785-791)
- Skips check for implicit aliases (node, stable, etc.) to preserve
  existing functionality
- Added unit tests to verify LTS names are rejected while version
  numbers still work
After this fix:
- `nvm install Argon` → fails (use `nvm install lts/argon` instead)
- `nvm install 4` → still works
- `nvm install node` → still works
- `nvm install lts/argon` → still works

This makes install and uninstall behavior consistent.

Fixes #3474.

nvm.sh

@@ -781,6 +781,15 @@ nvm_remote_version() {
   else
     VERSION="$(NVM_LTS="${NVM_LTS-}" nvm_remote_versions "${PATTERN}" | command tail -1)"
   fi
+
+  if [ -n "${PATTERN}" ] && [ "_${VERSION}" != "_N/A" ] && ! nvm_validate_implicit_alias "${PATTERN}" 2>/dev/null; then
+    local VERSION_NUM
+    VERSION_NUM="$(nvm_echo "${VERSION}" | command awk '{print $1}')"
+    if ! nvm_echo "${VERSION_NUM}" | nvm_grep -q "${PATTERN}"; then
+      VERSION='N/A'
+    fi
+  fi
+
   if [ -n "${NVM_VERSION_ONLY-}" ]; then
     command awk 'BEGIN {
       n = split(ARGV[1], a);