[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.

test/fast/Unit tests/nvm_remote_version

@@ -75,4 +75,24 @@ EXIT_CODE="$(nvm_remote_version node >/dev/null 2>&1 ; echo $?)"
   || die "nvm_remote_version node did not return contents of nvm_ls_remote node; got $OUTPUT"
 [ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version node did not exit with 0, got $EXIT_CODE"
 
+# Test LTS name rejection (Issue #3474)
+# When nvm_remote_versions returns a line with LTS name in description,
+# nvm_remote_version should reject it if the pattern doesn't match the version number
+
+nvm_remote_versions() {
+    echo "v4.9.1 Argon *"
+}
+OUTPUT="$(nvm_remote_version Argon)"
+EXIT_CODE="$(nvm_remote_version Argon >/dev/null 2>&1 ; echo $?)"
+[ "_$OUTPUT" = "_N/A" ] || die "nvm_remote_version Argon should return N/A (LTS name not in version), got $OUTPUT"
+[ "_$EXIT_CODE" = "_3" ] || die "nvm_remote_version Argon should exit with code 3, got $EXIT_CODE"
+
+nvm_remote_versions() {
+  echo "v4.9.1"
+}
+OUTPUT="$(nvm_remote_version 4)"
+EXIT_CODE="$(nvm_remote_version 4 >/dev/null 2>&1 ; echo $?)"
+[ "_$OUTPUT" = "_v4.9.1" ] || die "nvm_remote_version 4 should return v4.9.1, got $OUTPUT"
+[ "_$EXIT_CODE" = "_0" ] || die "nvm_remote_version 4 should exit with code 0, got $EXIT_CODE"
+
 cleanup