feat: IRM/AIP-protected file support

[sbroenne]

Summary

Adds support for opening IRM/AIP-protected Excel files that require Windows credential prompts.

Problem

IRM (Information Rights Management) / AIP (Azure Information Protection) protected Excel files could not be opened by ExcelMcp because:

1. The exclusive file lock check would fail before the Windows IRM auth dialog appeared
2. Files needed to be opened with Excel visible so the user could authenticate

Solution

• Auto-detect IRM files: Check OLE2 header magic bytes \D0 CF 11 E0 A1 B1 1A E1\ in \FileAccessValidator.IsIrmProtected()\
• Skip lock check for IRM files: Credential prompt must appear first
• Force \Visible=true\ for IRM files: Required for Windows IRM auth dialog
• Open read-only: IRM files opened with \ReadOnly:true\
• *Expose \isIrmProtected* in \ile(action='test')\ response
• Updated tool description with IRM workflow guidance

Changes

Core Implementation

• \src/ExcelMcp.ComInterop/FileAccessValidator.cs\ — \IsIrmProtected()\ via OLE2 header check
• \src/ExcelMcp.ComInterop/Session/ExcelBatch.cs\ — IRM branch: skip lock check, force Visible, open ReadOnly
• \src/ExcelMcp.Core/Models/ResultTypes.cs\ — \IsIrmProtected\ property on \FileValidationInfo\
• \src/ExcelMcp.Core/Commands/FileCommands.cs\ — Populate \IsIrmProtected\ in \Test()\
• \src/ExcelMcp.McpServer/Tools/ExcelFileTool.cs\ — Expose \isIrmProtected\ + IRM guidance in tool description

Also Included

• MCP SDK \

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None