Support native structured output through the shared execution contract

[SaladDay]

Sessions previously rejected every text.format=json_schema configuration, even when the native harness could execute it. This adds shared schema transport and a qualified Claude SDK path for single-agent environment:none execution with ordinary functions, preserving the native validated JSON and output identity through Items, SSE and cold continuation.

Core stays harness-neutral. Unqualified combinations reject explicitly; no model-output repair, prompt coercion, replacement loop or legacy compatibility is added. Saved Agent schemas remain lossless, including numeric constraints that the Claude runtime cannot execute exactly.

Validation:

• Pinned OpenAI Python SDK 3.13.0 and raw HTTP against real PostgreSQL/Core/gateway/daemon/Claude SDK 0.3.269/Kimi K3: function-only random value, structured output, receipts, ordered SSE, saved schema, restart and same-history continuation, cancellation, text regression and tenant isolation.
• Focused Go/SDK tests and regenerated make openapi.
• Final server make check and fresh independent GPT-6 Astra high whole-diff review passed. Regression also verifies a callback-free custom harness cannot dispatch previously queued structured work after qualification is removed, even when its Runtime still advertises support.

Scope/limits: Codex and MiniMax structured output, workspace/HTTP MCP/Subagent combinations and non-object roots remain unqualified. Claude's public Usage breakdown remains a known gap; native counters are retained. This is partial protocol coverage. Evidence: ~/.parsar/remediation/20260922/structured-output/ on zju_a100_2.

Validation scope: live model acceptance ran on 7f533d4; the shared dispatch qualification simplification in 697926d has dedicated PostgreSQL/gateway regression. Final candidate 0d6fc43 additionally updates the exported Runtime feature assertion and passes the full gate. Optional unrelated live-provider suites are not claimed as rerun. Failed intermediate logs are retained: one test-database ownership collision and one stale packaging feature assertion. The final gate used the database exclusively and retained the strict complete feature-list assertion.