Add versioned Skills and hosted template references

[SaladDay]

Callers can upload and version a Skill, reference it from hosted inline configuration or an Environment Template, and use it through native execution. Session creation authorizes and freezes the selected contents and concrete metadata, preserving existing Sessions and committed retries after source or template changes. Installation reuses the common V1 Runtime path.

The batch includes Skills/Versions/Content resources, encrypted bundles, reference initialization, generated SQL/OpenAPI, tests and documentation. Plugins, capability directories, new Provider/harness mechanisms and historical compatibility are excluded. Unverified upstream semantics and upload limits remain documented.

Validation:

• Dedicated PostgreSQL race checks, pinned official SDK 3.13.0 and raw HTTP resource checks.
• Codex/Kimi, Claude/Kimi and MiniMax Code/MiniMax real Docker workflows: upload, template reference, native Skill use, Files/Artifacts, tenant isolation, source deletion and cold continuation without reinstall/replay. All cleaned successfully.
• make sqlc-generate, make openapi, make check (484.22s), and diff checks passed. The optional unchanged MiniMax packaged-native probe was not enabled; actual deployment acceptance ran separately.
• Failed network/test-prompt attempts are retained in the linked contract acceptance records; no production workaround was added.

Review: user-authorized reused-context GPT-6 Astra high review covered all 52 changed files and original validation records, with no material actionable findings. The final documentation-only edit records that authorization accurately. This was not a fresh-context blind review and does not establish full protocol compatibility.