test(agents): remove jangar compatibility fixtures

[gregkonush]

Summary

• Removed stale JANGAR_* compatibility fixtures from Agents runtime, agentctl, and build/deploy tests.
• Kept canonical AGENTS_* coverage for controller config, gRPC config, image build args, and deploy helpers.
• Reworded leftover generic fixtures to domain-neutral terms while preserving explicit Agents/Jangar boundary guard tests.

Related Issues

None

Testing

• bun run --cwd services/agents test -- src/server/agent-resource-labels.test.ts src/server/supporting-primitives-controller.test.ts src/server/control-plane.test.ts src/server/__tests__/control-plane-runtime-admission.test.ts src/server/agents-controller/index.integration.test.ts src/server/v1/codex-runs.test.ts src/server/integrations-config.test.ts src/server/controller-runtime-config.test.ts src/server/control-plane-watch-reliability.test.ts src/server/__tests__/control-plane-grpc.test.ts src/server/agents-controller/runtime-config.test.ts
• bun run --cwd services/agents/agentctl test src/__tests__/config.test.ts
• bun test packages/scripts/src/agents/__tests__/build-image.test.ts packages/scripts/src/agents/__tests__/deploy-service.test.ts packages/scripts/src/agents/__tests__/resolve-agents-image-mode.test.ts
• bunx oxfmt --check services/agents/src/server/agent-resource-labels.test.ts services/agents/src/server/supporting-primitives-controller.test.ts services/agents/src/server/control-plane.test.ts services/agents/src/server/__tests__/control-plane-runtime-admission.test.ts services/agents/src/server/agents-controller/index.integration.test.ts services/agents/src/server/v1/codex-runs.test.ts services/agents/src/server/integrations-config.test.ts services/agents/src/server/controller-runtime-config.test.ts services/agents/src/server/control-plane-watch-reliability.test.ts services/agents/src/server/__tests__/control-plane-grpc.test.ts services/agents/src/server/agents-controller/runtime-config.test.ts services/agents/agentctl/src/__tests__/config.test.ts packages/scripts/src/agents/__tests__/build-image.test.ts packages/scripts/src/agents/__tests__/deploy-service.test.ts packages/scripts/src/agents/__tests__/resolve-agents-image-mode.test.ts
• rg -n "JANGAR_" services/agents packages/scripts/src/agents --glob '!**/node_modules/**'
• git diff --check

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed.
• Screenshots and Breaking Changes sections are handled appropriately.
• Documentation, release notes, and follow-ups are updated or tracked.