Require explicit service Harness qualification declarations

[SaladDay]

Service Harness profiles could omit capability flags or validation callbacks and still authorize admission. Require explicit support decisions and common-only or additional validation policies at catalog construction, rejecting missing, invalid and contradictory declarations before use.

Keep Runtime availability separate from service qualification, preserve Codex/Claude/MiniMax admission behavior and error precedence, and retain zero-value versus explicitly empty catalog semantics. Definition and validation stay in services/core/internal/engine/profile.go. Update the authoritative Harness guide and contributor owner index; do not restore the removed docs site. This changes no public API, model protocol, native adapter or deployment.

Final head: a5c0b69feed4eb87445c08b86bbbc47b220181ca, baseline 015d9f943446383c61e2163faf593f07a5a723e5.

Validation:

• Complete engine/execution suites with dedicated PostgreSQL and focused store/public onboarding tests passed on c9520ffe. Every changed Go file is byte-for-byte identical in the final head. Coverage includes missing fields, invalid values, policy/callback mismatches, placement/MCP combinations, immutable catalogs, admission precedence, message images and structured-output dispatch.
• c9520ffe also passed full make check, official-client acceptance and all native platforms. This is reusable code evidence, not a claim that final-head CI has completed.
• Final-head official-client acceptance passed. Native platform CI and full CI report their current status separately; existing runs continue.
• A fresh independent full-diff blind review of final head versus final baseline found no in-scope issues. Name guard and diff checks passed. No old module/directory or removed documentation-site files were restored.

Per the latest task instruction, targeted checks and necessary cross-module/database validation qualify this subtask; no additional duplicate full run is requested. The coordinating test chat owns final acceptance and merge, including required branch checks. These fixtures are not new live model qualification. No release, deployment or existing data changes.