fix: support gateway defaults for spawn and Docker Hub publish

[0xNyk]

Summary

• make /api/spawn compatible with OpenClaw agents that rely on configured default models by making model optional and only forwarding it when provided
• add regression coverage for spawn schema validation and gateway dashboard registration preserving device auth
• expand container release automation to publish the official multi-arch image to Docker Hub when Docker Hub credentials are configured, and correct the OCI source label/docs

Closes #430
Closes #431

Risk Level

Medium

Tests

• pnpm lint (passes with existing repo warnings outside this patch)
• pnpm typecheck
• pnpm test

Contribution Checklist

• Tests added/updated for behavior changes
• Lint/typecheck/build passing
• Security review done if auth/data/crypto touched
• DB migration tested if schema changed

Notes

• Docker Hub publishing is gated on repository secrets: DOCKERHUB_USERNAME and DOCKERHUB_TOKEN.
• main already included the runtime hardening that preserves gateway.controlUi.dangerouslyDisableDeviceAuth; this PR adds explicit regression coverage for that behavior and fixes the separate spawn-schema compatibility bug raised in Make 'model' optional in spawnAgentSchema to fix OpenClaw Gateway compatibility #430.

[github-actions]

📸 Screenshot Drift Check

This PR modifies UI source files. Please verify whether the README screenshots need refreshing:

• docs/mission-control-overview.png — main dashboard
• docs/mission-control-agents.png — agents panel
• docs/mission-control-memory-graph.png — memory graph

Changed UI files

src/app/api/spawn/route.ts

See docs/SCREENSHOT-GUIDE.md for instructions on capturing and optimising screenshots.

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