release(v2.1.3): fix Windows CI failure from v2.1.2's release build

v2.1.2's release CI failed on the Windows build leg: TestApplyHostsOverride_*
call applyHostsOverride(), which correctly refuses unconditionally on
non-Linux (hosts_override.go) -- but the tests didn't account for `go
test ./...` running on every platform the CI matrix builds for, only
Linux. Skip them on non-Linux with a clear reason instead.

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to the `theta-agent` daemon will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [v2.1.3] - 2026-08-10
+
+### Fixed
+- **v2.1.2's release build failed on the Windows CI leg.** `TestApplyHostsOverride_*` call `applyHostsOverride()`, which correctly refuses unconditionally on non-Linux — but the tests didn't skip themselves there, so `go test ./...` failed on the Windows build job. v2.1.2's actual code (the mDNS local-discovery feature itself) was never broken; only that release's CI run was. Tests now skip cleanly on non-Linux with a clear reason.
+
 ## [v2.1.2] - 2026-08-10
 
 ### Added

hosts_override_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -11,6 +12,14 @@ import (
 
 func withTempHostsFile(t *testing.T, initial string) string {
 	t.Helper()
+	// applyHostsOverride refuses unconditionally on non-Linux (see
+	// hosts_override.go) -- these tests exercise the Linux write path
+	// specifically, so they'd fail for the right reason on the Windows CI
+	// runner if not skipped. Confirmed the hard way: a real CI run failed
+	// here after this was missed.
+	if runtime.GOOS != "linux" {
+		t.Skip("applyHostsOverride is Linux-only; skipping on " + runtime.GOOS)
+	}
 	dir := t.TempDir()
 	path := filepath.Join(dir, "hosts")
 	if initial != "" {

telemetry.go

@@ -425,7 +425,7 @@ func collectHostDetails() HostDetails {
 	return details
 }
 
-const AgentVersion = "v2.1.2"
+const AgentVersion = "v2.1.3"
 
 // CollectDiscoveryData gathers static host information.
 func CollectDiscoveryData(cfg *Config) DiscoveryData {