feat(protocols): p.Service is the truthful service surface (V8 S4)

[marlon-costa-dc]

Slice S4 of plan V8 (bead flext-4jtcb.10), core step after the members (flext-web #106, flext-oracle-oic #112, flext-db-oracle #113 merged).

• p.Service declared five members no FlextService implements (service_info, valid, validate_business_rules, ok, fail_op), so isinstance(real_service, p.Service) was False.
• It now inherits the runtime surface from MixinsInfrastructure (declared once, R30: settings, container, context, logger, track, runtime seeds) and adds only execute.
• p.Executable (zero fleet uses, same phantom service_info) removed.
• The tautological isinstance-of-own-base test is replaced by the protocol contract and a negative case (a plain model is not a service).

Runtime: isinstance(Echo(), p.Service) is True (was False).
Local pre-push gate GREEN: gen (clean tree), audit, check, test.

🤖 Generated with Claude Code

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Summary by cubic

Makes p.Service match the surface every real service implements, so isinstance(real_service, p.Service) is now True instead of False.

• Inherits the runtime surface from MixinsInfrastructure and adds only execute, dropping five declared members that no service implements.
• Removes the unused p.Executable protocol, which carried the same phantom service_info.
• Replaces the tautological isinstance-of-own-base test with the protocol contract plus a negative case.

^{Written for commit e856965. Summary will update on new commits.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud