fix: handle package name without dot to prevent index out of range

[yashisrani]

Description

Fixes a potential index out of range panic in wrap/grpc.go when parsing proto files where the package name doesn't contain a dot.

Problem

When packageName has no dot (e.g., "mypackage"), strings.LastIndex returns -1, causing packageName[lastPiece+1:] to slice incorrectly and produce wrong output.

Solution

Added a check for lastPiece == -1 to handle package names without dots, ensuring correct slice indexing in all cases.

Changes

• wrap/grpc.go:471-478 - Fixed import alias extraction logic

Testing

• All existing tests pass
• Build compiles successfully

[yashisrani]

cc @coolwednesday @aryanmehrotra