Keep MCP model-output conversion on bound GitHub tools

bindRepository rebuilt each tool without the MCP client's toModelOutput
converter, so a model would receive the raw CallToolResult envelope.

Assistant-model: Claude Opus 5.5
Assistant-workflow: harness-stack (run f6f676b9-6506-489b-93e2-2616ea55c6a8)
Assistant-verification: bun test unit passed: new bindRepository toModelOutput test red without the fix, green with it; full suite 1556 pass, 2 skip
Assistant-verification: bun run ci passed: dprint, oxlint, tokens
Assistant-verification: bun run types passed: all workspaces and E2E
Co-authored-by: Alex Lavaee <lavaman131@github.com>