cmd: add --tools flag for MCP server integration

Integrate MCP servers with the ollama CLI and add route handlers for
tool-enabled chat completions.

CLI (cmd/cmd.go):
- Add --tools flag to 'ollama run' command
- Supports path argument: --tools /path/to/directory
- Multi-round tool execution loop with result display
- Displays available tools on startup

Routes (server/routes.go, server/routes_tools.go):
- MCP server handling in chat completions
- /api/tools endpoint for tool listing
- Session-based MCP manager lifecycle
- Detailed documentation of MCP integration flow

Parser (harmony/harmonyparser.go):
- Handle embedded <think> segments in tool call responses
- Extract tool calls from thinking model outputs

Relates to #7865

server/routes_tools.go

@@ -0,0 +1,91 @@
+package server
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/ollama/ollama/api"
+)
+
+// ToolsHandler handles requests to list available MCP tools.
+// GET: Returns available MCP server definitions from configuration.
+// POST with mcp_servers: Returns tools from the specified MCP servers.
+func (s *Server) ToolsHandler(c *gin.Context) {
+	var req struct {
+		MCPServers []api.MCPServerConfig `json:"mcp_servers,omitempty"`
+	}
+
+	if c.Request.Method == "POST" {
+		if err := c.BindJSON(&req); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+			return
+		}
+	}
+	
+	// If MCP servers provided, list their tools
+	if len(req.MCPServers) > 0 {
+		manager := NewMCPManager(10)
+		defer manager.Close()
+		
+		var allTools []ToolInfo
+		for _, config := range req.MCPServers {
+			if err := manager.AddServer(config); err != nil {
+				// Include error in response but continue
+				allTools = append(allTools, ToolInfo{
+					Name:        config.Name,
+					Description: "Failed to initialize: " + err.Error(),
+					Error:       err.Error(),
+				})
+				continue
+			}
+			
+			// Get tools from this server
+			tools := manager.GetAllTools()
+			for _, tool := range tools {
+				allTools = append(allTools, ToolInfo{
+					Name:        tool.Function.Name,
+					Description: tool.Function.Description,
+					Parameters:  &tool.Function.Parameters,
+					ServerName:  config.Name,
+				})
+			}
+		}
+		
+		c.JSON(http.StatusOK, ToolsResponse{
+			Tools: allTools,
+		})
+		return
+	}
+	
+	// Otherwise, list available MCP server definitions
+	defs, err := LoadMCPDefinitions()
+	if err != nil {
+		// Config parsing errors are client errors (bad config), not server errors
+		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid MCP configuration: " + err.Error()})
+		return
+	}
+
+	servers := defs.ListServers()
+	c.JSON(http.StatusOK, MCPServersResponse{
+		Servers: servers,
+	})
+}
+
+// ToolInfo provides information about a single tool
+type ToolInfo struct {
+	Name        string                      `json:"name"`
+	Description string                      `json:"description"`
+	Parameters  *api.ToolFunctionParameters `json:"parameters,omitempty"`
+	ServerName  string                      `json:"server,omitempty"`
+	Error       string                      `json:"error,omitempty"`
+}
+
+// ToolsResponse contains the list of available tools
+type ToolsResponse struct {
+	Tools []ToolInfo `json:"tools"`
+}
+
+// MCPServersResponse contains the list of available MCP server types
+type MCPServersResponse struct {
+	Servers []MCPServerInfo `json:"servers"`
+}