[MAINTENANCE] Consolidate duplicate VISSIM driver model code into shared base

[yunlishao-vibe]

Task Summary

DriverModel_RealSim.cpp and DriverModel_RealSim_v2021.cpp are nearly identical (~1887 and ~1922 lines respectively) with only minor API-level differences. Extract the shared logic into a common base to eliminate code duplication.

Why is this needed?

Currently any bug fix or feature must be applied to both files independently. The two files differ in only ~50 lines out of ~1900 (less than 3%), primarily:

• long vs int type for VISSIM API parameters (v2021 API uses int)
• A few global flags added to v2021: SUB_EGO_ONLY, ENABLE_WARMUP, isInitialTimeFinished
• Variable name simTime vs simTime_g
• Default value of NEED_SPEED_LIMIT (true vs false)

The remaining ~97% of code (message handling, socket communication, data processing, FIXS integration) is identical. Multiple // TODO: add code stubs appear in the same locations in both files.

Scope of Work

1. Analyze and document all differences

• Run a full diff and categorize every difference
• Document API-level differences (VISSIM 2022+ vs 2021 driver model API)

2. Extract shared logic

Option A: Single shared header DriverModel_FIXS_Common.h with inline implementation
Option B: Shared DriverModel_FIXS_Common.cpp compiled into both projects via shared source

3. Create thin version-specific wrappers

• DriverModel_RealSim.cpp → thin wrapper using modern VISSIM API (long parameters)
• DriverModel_RealSim_v2021.cpp → thin wrapper using legacy VISSIM API (int parameters)
• Both include/link to shared common implementation

4. Resolve TODO stubs

• The // TODO: add code stubs (at least 8 locations in each file) represent unimplemented message field handlers
• Document what each TODO means and either implement or remove with a proper issue reference

5. Add Python auto-test

• Add tests/Python/test_vissim_driver_parity.py that:
  • Parses both .cpp files
  • Verifies that non-API-signature sections are identical (or differ only in known documented ways)
  • Alerts if one file has a change that wasn't applied to the other

Files Involved

• ProprietaryFiles/VISSIMserver/DriverModel_RealSim/DriverModel_RealSim.cpp
• ProprietaryFiles/VISSIMserver/DriverModel_RealSim_v2021/DriverModel_RealSim_v2021.cpp
• ProprietaryFiles/VISSIMserver/VISSIMserver.sln
• Build scripts in scripts/dispatch/3_vissim_components.bat

Acceptance Criteria

• Shared common code extracted and not duplicated
• Both DLLs still build and function correctly
• tests/Python/test_vissim_driver_parity.py passes
• All TODO stubs addressed or converted to tracked issues
• Diff between the two wrapper files is ≤ 100 lines

Branch and PR Target

• All PRs for this issue should target the dev branch (not main)
• First ensure main is merged into dev before starting work