Package restructure and API changes, several fixes

- More emphasis on `api` package. It now holds database model structs
  from `lmcli/models` (which is now gone) as well as the tool spec,
  call, and result types. `tools.Tool` is now `api.ToolSpec`.
  `api.ChatCompletionClient` was renamed to
  `api.ChatCompletionProvider`.

- Change ChatCompletion interface and implementations to no longer do
  automatic tool call recursion - they simply return a ToolCall message
  which the caller can decide what to do with (e.g. prompt for user
  confirmation before executing)

- `api.ChatCompletionProvider` functions have had their ReplyCallback
  parameter removed, as now they only return a single reply.

- Added a top-level `agent` package, moved the current built-in tools
  implementations under `agent/toolbox`. `tools.ExecuteToolCalls` is now
  `agent.ExecuteToolCalls`.

- Fixed request context handling in openai, google, ollama (use
  `NewRequestWithContext`), cleaned up request cancellation in TUI

- Fix tool call tui persistence bug (we were skipping message with empty
  content)

- Now handle tool calling from TUI layer

TODO:
- Prompt users before executing tool calls
- Automatically send tool results to the model (or make this toggleable)

pkg/tui/views/chat/view.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"strings"
 
-	models "git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
+	"git.mlow.ca/mlow/lmcli/pkg/api"
 	"git.mlow.ca/mlow/lmcli/pkg/tui/styles"
 	tuiutil "git.mlow.ca/mlow/lmcli/pkg/tui/util"
 	"github.com/charmbracelet/lipgloss"
@@ -63,22 +63,22 @@ func (m Model) View() string {
 	return lipgloss.JoinVertical(lipgloss.Left, sections...)
 }
 
-func (m *Model) renderMessageHeading(i int, message *models.Message) string {
+func (m *Model) renderMessageHeading(i int, message *api.Message) string {
 	icon := ""
 	friendly := message.Role.FriendlyRole()
 	style := lipgloss.NewStyle().Faint(true).Bold(true)
 
 	switch message.Role {
-	case models.MessageRoleSystem:
+	case api.MessageRoleSystem:
 		icon = "⚙️"
-	case models.MessageRoleUser:
+	case api.MessageRoleUser:
 		style = userStyle
-	case models.MessageRoleAssistant:
+	case api.MessageRoleAssistant:
 		style = assistantStyle
-	case models.MessageRoleToolCall:
+	case api.MessageRoleToolCall:
 		style = assistantStyle
-		friendly = models.MessageRoleAssistant.FriendlyRole()
-	case models.MessageRoleToolResult:
+		friendly = api.MessageRoleAssistant.FriendlyRole()
+	case api.MessageRoleToolResult:
 		icon = "🔧"
 	}
 
@@ -139,21 +139,21 @@ func (m *Model) renderMessage(i int) string {
 	}
 
 	// Show the assistant's cursor
-	if m.state == pendingResponse && i == len(m.messages)-1 && msg.Role == models.MessageRoleAssistant {
+	if m.state == pendingResponse && i == len(m.messages)-1 && msg.Role == api.MessageRoleAssistant {
 		sb.WriteString(m.replyCursor.View())
 	}
 
 	// Write tool call info
 	var toolString string
 	switch msg.Role {
-	case models.MessageRoleToolCall:
+	case api.MessageRoleToolCall:
 		bytes, err := yaml.Marshal(msg.ToolCalls)
 		if err != nil {
 			toolString = "Could not serialize ToolCalls"
 		} else {
 			toolString = "tool_calls:\n" + string(bytes)
 		}
-	case models.MessageRoleToolResult:
+	case api.MessageRoleToolResult:
 		if !m.showToolResults {
 			break
 		}
@@ -221,11 +221,11 @@ func (m *Model) conversationMessagesView() string {
 		m.messageOffsets[i] = lineCnt
 
 		switch message.Role {
-		case models.MessageRoleToolCall:
+		case api.MessageRoleToolCall:
 			if !m.showToolResults && message.Content == "" {
 				continue
 			}
-		case models.MessageRoleToolResult:
+		case api.MessageRoleToolResult:
 			if !m.showToolResults {
 				continue
 			}
@@ -251,9 +251,9 @@ func (m *Model) conversationMessagesView() string {
 	}
 
 	// Render a placeholder for the incoming assistant reply
-	if m.state == pendingResponse && (len(m.messages) == 0 || m.messages[len(m.messages)-1].Role != models.MessageRoleAssistant) {
-		heading := m.renderMessageHeading(-1, &models.Message{
-			Role: models.MessageRoleAssistant,
+	if m.state == pendingResponse && (len(m.messages) == 0 || m.messages[len(m.messages)-1].Role != api.MessageRoleAssistant) {
+		heading := m.renderMessageHeading(-1, &api.Message{
+			Role: api.MessageRoleAssistant,
 		})
 		sb.WriteString(heading)
 		sb.WriteString("\n")