Update ProtoBuf to 1.x and regenerate protobuf definitions

[KristianHolme]

Note: This PR was authored with Cursor (AI-assisted coding).

Summary

Fixes the ProtoBuf.jl deprecation warning:

You are using code generated by an older version of ProtoBuf.jl, which was deprecated. Please regenerate your protobuf definitions with the current version of ProtoBuf.jl.

• Regenerate src/protojl/ with ProtoBuf.jl 1.3 (new decode(d, T, _endpos, _group) API)
• Bump compat: ProtoBuf 1.0.11 → 1, Julia 1.6 → 1.10 (required by ProtoBuf 1.3)
• Source fixes for the new codegen:
  • Restore plugin module names (tensorboard_plugin_text, etc.) after regeneration
  • Update hparams.jl for new HParamInfo.differs field
  • Remove obsolete custom Dict encode/decode workarounds (ProtoBuf 1.3 handles maps natively)
  • Drop dead writeproto / legacy hasproperty code
• Codegen tooling: compile_proto.jl now replaces existing output and renames plugin modules; download_proto_source fixes Linux sed for struct.proto → struct_tb.proto

Test plan

• Pkg.test() — 166 passed, 1 failed (optional Plots PNG bytes), 1 broken (Graph Logger; pre-existing)
• All hparams tests pass (encode/decode round-trip verified)
• No ProtoBuf deprecated-codegen warning on load/encode

Made with Cursor