fix: correct comments that framed preview as canonical over beta

beta is the canonical lifecycle term; preview is a backward-compat
alias. Several comments had the relationship inverted.

Author: daniel-garcia

internal/config/lifecycle.go

@@ -40,7 +40,7 @@ func NormalizeLifecycle(lifecycle string) string {
 // Rules:
 //
 //	experimental → must have -alpha.* prerelease
-//	beta/preview → must have -alpha.*, -beta.*, or -rc.* prerelease
+//	beta (or preview alias) → must have -alpha.*, -beta.*, or -rc.* prerelease
 //	stable       → must NOT have a prerelease tag
 //	deprecated   → any version allowed (warning emitted by caller)
 //	sunset       → blocked unless override is set
@@ -117,7 +117,7 @@ func LifecycleRequiresWarning(lifecycle string) bool {
 var lifecycleOrder = map[string]int{
 	"experimental": 0,
 	"preview":      1,
-	"beta":         1, // alias — same rank as preview
+	"beta":         1, // canonical; preview is a backward-compat alias
 	"stable":       2,
 	"deprecated":   3,
 	"sunset":       4,

internal/config/version.go

@@ -242,7 +242,7 @@ func ValidateVersionLine(version, line string) error {
 //
 // The lifecycle parameter is used to attach the correct prerelease tag:
 //   - "experimental" → -alpha.1
-//   - "preview"/"beta" → -beta.1
+//   - "beta" → -beta.1 ("preview" accepted as alias)
 //   - "stable" → no prerelease
 //   - "deprecated" → no prerelease (but caller should warn)
 //   - "sunset" → blocked

internal/config/version_test.go

@@ -362,7 +362,7 @@ func TestLifecyclePrerelease(t *testing.T) {
 	assert.Equal(t, "alpha.1", lifecyclePrerelease("experimental", 1))
 	assert.Equal(t, "alpha.3", lifecyclePrerelease("experimental", 3))
 	assert.Equal(t, "beta.1", lifecyclePrerelease("preview", 1))
-	assert.Equal(t, "beta.1", lifecyclePrerelease("beta", 1)) // alias for preview
+	assert.Equal(t, "beta.1", lifecyclePrerelease("beta", 1)) // canonical form
 	assert.Equal(t, "", lifecyclePrerelease("stable", 1))
 	assert.Equal(t, "", lifecyclePrerelease("deprecated", 1))
 	assert.Equal(t, "", lifecyclePrerelease("", 1))