fix: standardize bond link selection method JSON field naming

Adds support for "linkSelectMethod" as the JSON configuration field name
while maintaining backward compatibility with the legacy "activeReselect"
field name.

This change aligns the JSON field name with the internal API naming
convention (setLinkSelectMethod/getLinkSelectMethod) and follows the
established pattern in the codebase where JSON field names match their
corresponding setter method names.

The implementation:
- Checks for the new field name first, then falls back to the legacy name
- Emits a deprecation warning when "activeReselect" is used
- Ensures existing configurations continue to work without modification

Resolves terminology inconsistency identified in docs PR #263

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

service/OneService.cpp

@@ -2612,7 +2612,17 @@ class OneServiceImpl : public OneService {
 					}
 					_node->bondController()->addCustomLink(customPolicyStr, new Link(linkNameStr, ipvPref, mtu, capacity, enabled, linkMode, failoverToStr));
 				}
-				std::string linkSelectMethodStr(OSUtils::jsonString(customPolicy["activeReselect"], "always"));
+				// Check for new field name first, fall back to legacy field name for backward compatibility
+				std::string linkSelectMethodStr;
+				if (customPolicy.contains("linkSelectMethod")) {
+					linkSelectMethodStr = OSUtils::jsonString(customPolicy["linkSelectMethod"], "always");
+				} else {
+					linkSelectMethodStr = OSUtils::jsonString(customPolicy["activeReselect"], "always");
+					if (customPolicy.contains("activeReselect")) {
+						fprintf(stderr, "warning: 'activeReselect' is deprecated, please use 'linkSelectMethod' instead in policy '%s'\n", customPolicyStr.c_str());
+					}
+				}
+				
 				if (linkSelectMethodStr == "always") {
 					newTemplateBond->setLinkSelectMethod(ZT_BOND_RESELECTION_POLICY_ALWAYS);
 				}