Migrate opencode + omp + zcode clients to Provider Injection

[NOirBRight]

This was generated by AI during triage.

Summary

Migrate opencode, omp, and zcode from Managed Takeover to Provider Injection. Phase 4 of campaign 0.1.9 (target 0.1.9-beta4).

Scope

opencode (largest delta — full overwrite today)

• opencode_config_text (gateway.rs:5725-5787) currently emits a complete file containing only codexhub providers. Change to surgical edit of the existing opencode.json: insert/update the codexhub provider entry, preserve all foreign keys and providers.
• Stop forcing model/small_model; activation becomes user-owned.

omp

• models.yml: stop full overwrite (omp_models_yml_text, gateway.rs:5936-5971); insert codexhub providers preserving foreign ones.
• config.yml: modelRoles handling already surgical — stop forcing default role to codexhub; activation user-owned.

zcode

• config.json provider map is already surgical — mostly readback-semantics migration to block fingerprint.
• codexhub.json catalog + cache are CodexHub-owned separate files; full overwrite of own files is compatible with coexistence — keep, but document ownership boundary.

Existing managed users

• Same migration path as beta3: first Apply after upgrade restores pre-takeover backup, then injects.

Acceptance criteria

• Each client preserves foreign providers/settings through apply/detach cycles
• detach removes only the injected block (+ credential), verified by block-fingerprint readback
• real-client E2E matrix re-qualified for all three clients under injection semantics

Related

• Add DeepSeek Harness (DSH) as CodexHub's fifth fully supported managed client #430, ADR-0004