Update proto based on nebu development

[tmosleyIII]

This pull request updates the Go toolchain and dependencies, refreshes generated protobuf and gRPC files, and improves the proto generation process in the build system. The main changes are grouped below.

Toolchain and Dependency Upgrades:

• Upgraded Go version to 1.26.x in flake.nix and go.mod, and updated all related dependencies (gRPC, protobuf, and others) to their latest versions. [1] [2]

Build System Improvements:

• Added support for generating "ingest" protos via a new proto-ingest Makefile target, ensuring shared types are generated and integrated before legacy proto generation. [1] [2]

Protobuf and gRPC Code Generation:

• Regenerated all generated Go files (go/gen/...) using the updated toolchain and dependencies, resulting in updated version headers and minor code changes for compatibility. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

gRPC API Consistency and Minor Fixes:

• Standardized error returns in all unimplemented gRPC service methods to use status.Error instead of status.Errorf, and fixed typos in comments (e.g., "pancis" → "panics"). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Protobuf Import Path Correction:

• Fixed the import path for token_transfer in go/gen/flow/v1/envelope.pb.go to ensure correct referencing of shared ingest types.