Add Reflog and History MCP Tools

[bbarker]

Overview

Adds two new MCP tools to expose Unison's reflog and history functionality to AI agents:

• reflog - Get branch state change history (wraps UCM reflog command)
• history - Get causal history with diffs (wraps UCM history command)

reflog tool arguments:

{
  "projectContext": { "projectName": "@user/project", "branchName": "main" },
  "scope": "branch" | "project" | "global",  // optional, default "branch"
  "limit": 100   // optional, default 100
}

history tool arguments:

{
  "projectContext": { "projectName": "@user/project", "branchName": "main" },
  "startHash": "#abc123...",  // optional
  "limit": 100,               // optional, uses UCM history default
  "diffLimit": 10             // optional, uses UCM history default
}

Implementation notes

• reflogTool: Uses Codebase.getProjectBranchReflog, getProjectReflog, and getGlobalReflog - same functions as UCM reflog command. Returns structured JSON.

• historyTool: Uses handleInputMCP with Input.HistoryI - same handler as UCM history command. Returns UCM-formatted text output.

• No core file modifications: Only added code to MCP/Types.hs and MCP/Tools.hs.

Test coverage

Tested manually via MCP tool invocations on a local project after restarting the unison mcp server from claude code.

[aryairani]

Could you add an mcp transcript test to unison-src/transcripts/idempotent/mcp.md? Ping me back if any concerns.

[bbarker]

Thanks @ChrisPenner - rebased