[Feature]: TypeScript 6 compatibility

## Feature Request

**Is your feature request related to a problem?**

`ts-jest@29` declares `peerDependencies: { "typescript": ">=4.3 <6" }`, which blocks projects from upgrading to TypeScript 6.0. When running `npm install` with `typescript@^6.0.2`, npm logs:

\`\`\`
npm warn Could not resolve dependency:
npm warn peer typescript@">=4.3 <6" from ts-jest@29.4.6
\`\`\`

TypeScript 6 shipped as stable and introduces several changes relevant to ts-jest:
- New default compiler options (`strict: true`, `moduleResolution: bundler`, `target: es2025`, `types: []`)
- `rootDir` is now required to be explicit when the inferred root is ambiguous (TS5011)
- `module: commonjs` + `moduleResolution: bundler` combination now allowed

**Describe the solution you'd like**

Update `ts-jest` to declare compatibility with TypeScript 6, either:
1. A `29.x` patch that widens the peer dep range to `>=4.3 <7` and addresses any TS6 internal API changes, or
2. A new `30.x` major release tracking TypeScript 6+ support

**Additional context**

- TypeScript 6 release: https://devblogs.microsoft.com/typescript/announcing-typescript-6-0/
- `typescript-eslint` has a similar open compatibility gap for TS6
- The project I hit this on uses `vitest` as the primary test runner so `ts-jest` is secondary — but the peer dep warning is a real blocker for any Jest-first project trying to adopt TS6

**Versions**
- ts-jest: 29.4.6
- TypeScript: 6.0.2
- Node: 25.8.1

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