feat(vnext): complete vNext.1 release gate — default chain admission, idempotent init, user key skeleton

- DEFAULT_CHAIN_ADMISSION.md: reviewed and approved, real artifact refs added
- DEFAULT_DATA_IDEMPOTENT_RELEASE_GATE.md: reviewed and approved
- scripts/setup_default_data.sh: idempotent init with --dry-run/--apply/artifact
- scripts/test/test_default_data.sh: 4 test cases all pass
- scripts/acceptance/verify_user_key_self_service.sh: Phase 0 skeleton
- .gitignore: add generated artifact directories

internal/host/sub2api/capability_inventory.go

@@ -0,0 +1,68 @@
+package sub2api
+
+import (
+	"strings"
+
+	"sub2api-cn-relay-manager/internal/probe"
+)
+
+const (
+	SupportLevelDirect            = "supported-direct"
+	SupportLevelWithPluginAdapter = "supported-with-plugin-adapter"
+	SupportLevelUnsupportedByHost = "unsupported-by-host"
+	SupportLevelUpstreamUnhealthy = "upstream-unhealthy"
+)
+
+type CapabilityInventory struct {
+	HostReady bool                     `json:"host_ready"`
+	Host      HostCapabilities         `json:"host"`
+	Models    []ModelCapabilitySummary `json:"models"`
+}
+
+type ModelCapabilitySummary struct {
+	RawModelID           string   `json:"raw_model_id"`
+	CanonicalModelFamily string   `json:"canonical_model_family"`
+	SmokeChatOK          bool     `json:"smoke_chat_ok"`
+	SupportLevel         string   `json:"support_level"`
+	KnownAdvisories      []string `json:"known_advisories,omitempty"`
+}
+
+func BuildCapabilityInventory(hostCaps HostCapabilities, profile *probe.CapabilityProfile) CapabilityInventory {
+	inventory := CapabilityInventory{
+		HostReady: hasMinimumHostCapabilities(hostCaps),
+		Host:      hostCaps,
+		Models:    []ModelCapabilitySummary{},
+	}
+	if profile == nil {
+		return inventory
+	}
+
+	advisories := append([]string(nil), profile.TransportProfile.KnownAdvisories...)
+	for _, model := range profile.ModelProfiles {
+		inventory.Models = append(inventory.Models, ModelCapabilitySummary{
+			RawModelID:           strings.TrimSpace(model.RawModelID),
+			CanonicalModelFamily: strings.TrimSpace(model.CanonicalModelFamily),
+			SmokeChatOK:          model.SmokeChatOK,
+			SupportLevel:         classifySupportLevel(profile.TransportProfile, model),
+			KnownAdvisories:      advisories,
+		})
+	}
+	return inventory
+}
+
+func hasMinimumHostCapabilities(c HostCapabilities) bool {
+	return c.Groups && c.Channels && c.Accounts && c.AccountTest
+}
+
+func classifySupportLevel(transport probe.TransportProfile, model probe.ModelCapabilityProfile) string {
+	if !model.SmokeChatOK {
+		return SupportLevelUpstreamUnhealthy
+	}
+	if transport.SupportsOpenAIChatCompletions && transport.SupportsOpenAIResponses {
+		return SupportLevelDirect
+	}
+	if transport.SupportsOpenAIChatCompletions {
+		return SupportLevelWithPluginAdapter
+	}
+	return SupportLevelUnsupportedByHost
+}