Wrap chunk content in a Chunk type

Preparing to include additional information with each chunk (e.g. token
count)

pkg/tui/views/chat/chat.go

@@ -4,6 +4,7 @@ import (
 	"time"
 
 	models "git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
+	"git.mlow.ca/mlow/lmcli/pkg/lmcli/provider"
 	"git.mlow.ca/mlow/lmcli/pkg/tui/shared"
 	"github.com/charmbracelet/bubbles/cursor"
 	"github.com/charmbracelet/bubbles/spinner"
@@ -16,7 +17,7 @@ import (
 // custom tea.Msg types
 type (
 	// sent on each chunk received from LLM
-	msgResponseChunk string
+	msgResponseChunk provider.Chunk
 	// sent when response is finished being received
 	msgResponseEnd string
 	// a special case of common.MsgError that stops the response waiting animation
@@ -82,7 +83,7 @@ type Model struct {
 	editorTarget    editorTarget
 	stopSignal      chan struct{}
 	replyChan       chan models.Message
-	replyChunkChan  chan string
+	replyChunkChan  chan provider.Chunk
 	persistence     bool // whether we will save new messages in the conversation
 
 	// ui state
@@ -114,7 +115,7 @@ func Chat(shared shared.Shared) Model {
 
 		stopSignal:     make(chan struct{}),
 		replyChan:      make(chan models.Message),
-		replyChunkChan: make(chan string),
+		replyChunkChan: make(chan provider.Chunk),
 
 		wrap:            true,
 		selectedMessage: -1,