[Nexthop] wedge800cact - add sdkVersion to hw test config

[vvasavada-nexthop]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

Add the sdkVersion placeholder block to wedge800cact.agent.materialized_JSON so that
MultiSwitchAgentEnsemble::isSai() passes in multi_switch mode.

getSw()->getSdkVersion() is sourced only from the SwitchConfig's sdkVersion field. Without it, isSai() aborts on
CHECK(sdkVersion.has_value() && sdkVersion.value().asicSdk().has_value()) for any test whose initialConfig invokes ensemble.isSai.

Test Plan

Verified no SIGABRT after the fix on Wedge800CACT box. Consistently ran into SIGABRT for the same testlets without the fix.

Without the fix:

# no sdkVersion in config file
[dut]# grep "sdkVersion" share/hw_test_configs/wedge800cact.agent.materialized_JSON

# test run
[dut]# ./bin/run_test.py sai_agent --config ./share/hw_test_configs/wedge800cact.agent.materialized_JSON   --skip-known-bad-tests leaba/25.11.4210/25.11.4210/graphene202x   --filter="AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced" --fboss_logging DBG9 > /home/netops/test.log 2>&1

# check failed SIGABRT
[dut]# grep "Check failed" /home/netops/test.log
F20260701 23:32:01.650077 46845 MultiSwitchAgentEnsemble.cpp:48] Check failed: sdkVersion.has_value() && sdkVersion.value().asicSdk().has_value()

# test failed
[dut]# grep "FAIL" /home/netops/test.log
########## Coldboot test results (1/1): [ FAILED ] cold_boot.AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced (764 ms)
[ FAILED ] cold_boot.AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced (764 ms)
   FAILED : 1

With the fix:

# sdkVersion in config file
[dut]# grep "sdkVersion" share/hw_test_configs/wedge800cact.agent.materialized_JSON
    "sdkVersion": {
    
 # test run
[dut]# ./bin/run_test.py sai_agent --config ./share/hw_test_configs/wedge800cact.agent.materialized_JSON   --skip-known-bad-tests leaba/25.11.4210/25.11.4210/graphene202x   --filter="AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced" --fboss_logging DBG9 > /home/netops/test.log 2>&1

# no check failed. No SIGABRT
[dut]#grep "Check failed" /home/netops/test.logg

# no failures
[dut]# grep "FAIL" /home/netops/test.log
   FAILED : 0
   

# tests passed
[dut]# grep "PASS" /home/netops/test.log
[  PASSED  ] 1 test.
[  PASSED  ] 1 test.
[ PASSED ] cold_boot.AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced (22595 ms)
[ PASSED ] warm_boot.AgentLinkLocalForwardingTest.EcmpLinkLocalNexthopsLoadBalanced (4767 ms)
   PASSED : 2