Port Bun workspace-relative tarballs and nested placement

Context

Port the next sorted Bun package-manager boundary in cli/install/bun-workspaces.test.ts.

Parent tracker: #66

Completed scope

• Resolve workspace-relative .tgz paths against the owning workspace.
• Preserve archive package identity/version when installed through an alias path.
• Pass the concurrent 6-workspace / 12-tarball regression without mutable graph lookups from archive workers.
• Materialize conflicting dependencies beneath the installed workspace package.
• Emit the current v2 text lockfile format for matching workspace devDependency/npm peerDependency graphs.
• Ratchet the untouched file at 63 passed / 0 failed / 0 unsupported / 0 TODO.

Completed on main in 4b1c17e.

Verification:

• untouched cli/install/bun-workspaces.test.ts: 63 passed / 0 failed / 0 unsupported / 0 TODO
• relative and CLI tarballs preserve qux@0.0.2
• all 12 concurrent renamed workspace tarballs install as bar@0.0.2
• conflicting bar@0.0.7 is placed beneath the installed boba workspace package
• matching workspace dev/npm peer graph emits lockfile v2
• full home_test gate: exit code 0