feat: support 32-bit Office environments (AnyCPU build + ACE provider auto-detection)

[KoyaMuramatsu]

Problem

Users with 32-bit Microsoft Office installed cannot use this server.

Microsoft's policy forbids installing the 64-bit ACE redistributable alongside 32-bit Office — they must match in bitness. Since the server is currently built as x64 and hardcodes Microsoft.ACE.OLEDB.16.0, it fails entirely on machines with 32-bit Office, which is still very common in enterprise environments.

Error observed:

Provider cannot be found. It may not be properly installed.

Solution

Two changes make the server work transparently in both environments:

1. AnyCPU build target

Changed PlatformTarget from x64 to AnyCPU and removed the win-x64 RuntimeIdentifier. This allows the process to run as 32-bit on systems where 32-bit ACE is the only option.

2. OleDB provider auto-detection

Instead of hardcoding Microsoft.ACE.OLEDB.16.0, the server now:

1. Checks AccessMcp:OleDbProvider in appsettings.json (explicit override)
2. Probes ACE.OLEDB.16.0 — uses it if available (64-bit systems)
3. Falls back to ACE.OLEDB.12.0 — used on 32-bit Office systems
4. Logs a clear warning if neither provider is found

This is implemented in:

• OleDbService.DetectOleDbProvider() — used by all data operations
• ComInteropService.ResolveOleDbConnectionString() — used by VBA/COM tools

3. Explicit override via appsettings.json

Users who need to pin a specific provider can set:

{
  "AccessMcp": {
    "OleDbProvider": "Microsoft.ACE.OLEDB.12.0"
  }
}

Files Changed

File	Change
MS.Access.MCP.Server.csproj	x64 → AnyCPU, removed RuntimeIdentifier
OleDbService.cs	Added DetectOleDbProvider() with 16.0→12.0 fallback
ComInteropService.cs	Added ResolveOleDbConnectionString() with same logic
AccessMcpOptions.cs	Added OleDbProvider property
appsettings.json	Exposed OleDbProvider: null (auto-detect default)

Compatibility

Environment	Before	After
64-bit Office / ACE 16.0	✅ Works	✅ Works (same behavior)
32-bit Office / ACE 12.0	❌ Fails	✅ Works
No ACE installed	❌ Fails	❌ Fails (with clear warning message)

Note: Local build verification was blocked by a corporate proxy. The logic change is minimal and follows standard .NET OleDB provider probing patterns. Happy to adjust if CI surfaces issues.