[0x0021]

Summary

Proxy import reduced a subscription to its proxies only. When a payload was extracted node-by-node, the airport's dns.nameserver-policy and dns.proxy-server-nameserver-policy were discarded along with the rest of the dns section, so the airport's DNS routing policy never reached the running configuration.

This adds both tables to the import report so the caller can carry them into the main configuration:

• proxyImportReport.DNSNameServerPolicy / DNSProxyServerNameserverPolicy, both omitempty
• extractProxyImportDNSPolicy lifts them from a decoded mihomo document
• JSON configuration containers (mihomo-json) are decoded for their dns section too; the YAML path already holds the decoded document

No merge semantics change here. MergeOverrideForIOS already unions these maps with the user's own patch on the winning side, so the client only had to stop throwing the data away.

A payload without a dns section reports exactly what it did before, and the report encoding is unchanged for existing consumers (encodeProxyImportReport marshals the struct as a whole).

Testing

go build ./...
go vet ./
gofmt -l .
go test ./ -run 'TestProxyImport' -count=1

New tests in bind/clash/proxy_import_dns_test.go:

• TestProxyImportCarriesDNSNameServerPolicy — YAML payload, both tables extracted
• TestProxyImportCarriesDNSNameServerPolicyFromJSONContainer — mihomo-json payload reaches the same tables
• TestProxyImportWithoutDNSLeavesPolicyNil — no dns section leaves both nil
• TestProxyImportDNSMergesUnderUserOverride — end-to-end: the airport table reaches the node document, then mergeOverrideDocument unions it with a user patch so shared domains resolve to the user's entry while airport-only domains survive

go test ./ -count=1 reports two failures, TestBindClashInitStaysWithinItsBudget and TestJSONToYamlRefusesRunawayNesting. Both fail identically on the unmodified base commit (verified via git stash), so they are pre-existing and unrelated to this change.

Related client-side change: ProjectClash/Clash-Client#56