Run gRPC tools on the client

[devproje]

What this changes

Moves the native gRPC client closer to a local coding-agent model while keeping inference and session state on the server.

• Records an explicit client or server mode while preserving legacy paired configurations
• Reads agents, skills, sessions, and usage from the paired server in client mode
• Advertises client builtin and MCP tool definitions over the bidirectional chat stream
• Sends model tool calls to the client for local execution and returns results to the server model loop
• Keeps dangerous-tool approval in the local TUI and refuses dangerous tools in non-interactive prompt mode
• Persists remote tool progress and results in the server-owned session
• Roots Discord administrator file, search, and shell tools at the server user's home directory without changing process cwd
• Updates the protobuf contract, generated sources, tests, README, and architecture documentation

How it was verified

• make test-race passes
• New behaviour has a test, or there is nothing to test
• make build passes

Checklist

• Follows docs/CONVENTION.md: no comments, no :=, one var block per function in first-use order with err last, callees before callers, and main unconditionally last
• New .go files carry the two-line SPDX header
• Documentation updated if behaviour a user can see has changed
• My contribution is licensed GPL-3.0-or-later, matching the project