[openapi-diff-runner] Support renamed files in breaking change detection

[Copilot]

The openapi-diff-runner was treating renamed files as separate additions and deletions, causing unnecessary dummy file creation and incorrect breaking change comparisons.

Changes

Core logic (command-helpers.ts)

• Return renames array instead of flattening into additions/deletions
• Auto-detect renames missed by git: when exactly one deletion and one addition exist in the same folder, treat as rename
• Update return type to include renames: { from: string; to: string }[]

Breaking change detection (detect-breaking-change.ts, commands.ts)

• Pass renamedSwaggers through detection context
• Compare renamed files old-to-new instead of old-to-empty and empty-to-new
• Eliminates false dummy file creation for simple renames

Example behavior

Before:

// Renaming foo.json → openapi.json produced:
{
  additions: ["openapi.json"],  // compared against empty
  deletions: ["foo.json"],       // compared against empty
  renames: []
}

After:

{
  additions: [],
  deletions: [],
  renames: [{ from: "foo.json", to: "openapi.json" }]  // compared directly
}

This handles Git-detected renames, case-only folder changes, and add/delete pairs that represent renames.

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[mikeharder]

dup of #40303