feat: add cluster execution owner contract

[acedatacloud-dev]

Summary

• add the generic X-Ace-Execution-Owner: x402 execute-only contract
• skip worker /record only for the recognized owner; unknown/missing owners keep normal recording
• add case-insensitive dict and real Tornado header tests plus PR CI

Hard dependency

Do not merge or publish this package until https://github.com/AceDataCloud/PlatformGateway/pull/214 is merged and deployed. The public Kong boundary must strip client-supplied owner headers first.

Validation

• 5 unit tests passed on Python 3.11
• sdist and wheel built successfully
• wheel contains acedatacloud_scaffold/execution.py
• public imports and compileall passed

🤖 对抗评审 (reviewer: Explore, 2 rounds)

• RISK: case-sensitive mapping lookup → fixed with case-insensitive header iteration and real Tornado coverage
• RISK: public clients could spoof execution ownership → fixed by hard dependency on Gateway PR #214; this PR remains Draft until that boundary is deployed
• RISK: unknown owners silently bypass policy → rebutted: unknown owners retain normal billing; added warning for observability
• RISK: pre-existing logger.catch and duplicate initializer → out of scope; neither is introduced nor exercised by the skip path