feat: scaffold @metamask/bitcoin-regtest-up package

[ulissesferreira]

Summary

This PR is the first of two PRs splitting #8827 into cleanly-reviewable pieces.

It contains only the pure scaffold output of yarn create-package plus ownership configuration — zero implementation logic.

What's included

• packages/bitcoin-regtest-up/ — scaffolded package skeleton (source placeholder, tests, CHANGELOG, README, LICENSE, jest/tsconfig configs) generated by yarn create-package --name bitcoin-regtest-up --description "Bitcoin Core regtest runtime installer for MetaMask E2E tests"
• tsconfig.json / tsconfig.build.json — monorepo-level references updated by the tool
• yarn.lock — updated by yarn install run inside the tool
• README.md — package list updated by yarn readme-content:update
• .github/CODEOWNERS — ownership entries for the package (alphabetical list after foundryup + Package Release section), mirroring the foundryup/solana-test-validator-up pattern with @MetaMask/networks added
• teams.json — issue-label routing entry, directly after the foundryup entry

What's NOT included

No implementation source, no bin field, no new runtime dependencies, no knip.config.ts changes, no unrelated monorepo churn.

Stacked PR

The implementation (real installer source, CLI bin, tests, full README) follows in a stacked PR based on this branch.

Verification

yarn workspace @metamask/bitcoin-regtest-up run build
yarn workspace @metamask/bitcoin-regtest-up run test
yarn constraints
yarn lint:teams
yarn readme-content:check

All passed ✓

---

Note

Low Risk
Scaffold and metadata-only changes; placeholder export does not affect production wallet or network behavior.

Overview
Adds @metamask/bitcoin-regtest-up to the monorepo as a scaffold-only workspace (intended future Bitcoin Core regtest runtime installer for E2E tests). The diff is yarn create-package output plus ownership wiring—no installer logic, no bin, and no new runtime dependencies.

Monorepo integration: root tsconfig.json / tsconfig.build.json references, yarn.lock, and root README.md package list + mermaid graph include the new package.

Governance: .github/CODEOWNERS and teams.json assign joint ownership after foundryup (mobile/extension platforms, plus @MetaMask/networks and core-platform on release paths), mirroring similar E2E tooling packages.

Package contents: standard skeleton (LICENSE, CHANGELOG, jest/tsconfig/typedoc, build scripts) with placeholder src/index.ts / test greeter until a follow-up PR lands real implementation.

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