Introduce "agents"

An agent is currently a name given to a system prompt and a set of
tools which the agent has access to.

This resolves the previous issue of the set of configured tools being
available in *all* contexts, which wasn't always desired. Tools are now
only available when an agent is explicitly requested using the
`-a/--agent` flag.

Agents are expected to be expanded on: the concept of task-specilized
agents (e.g. coding), the ability to define a set of files an agent
should always have access to for RAG purposes, etc.

Other changes:

- Removes the "tools" top-level config structure (though this is expected
to come back along with the abillity to define custom tools).

- Renamed `pkg/agent` to `pkg/agents`

pkg/agents/toolbox/write_file.go

@@ -0,0 +1,71 @@
+package toolbox
+
+import (
+	"fmt"
+	"os"
+
+	toolutil "git.mlow.ca/mlow/lmcli/pkg/agents/toolbox/util"
+	"git.mlow.ca/mlow/lmcli/pkg/api"
+)
+
+const WRITE_FILE_DESCRIPTION = `Write the provided contents to a file relative to the current working directory.
+
+Example result:
+{
+	"message": "success"
+}`
+
+var WriteFileTool = api.ToolSpec{
+	Name:        "write_file",
+	Description: WRITE_FILE_DESCRIPTION,
+	Parameters: []api.ToolParameter{
+		{
+			Name:        "path",
+			Type:        "string",
+			Description: "Path to a file within the current working directory to write to.",
+			Required:    true,
+		},
+		{
+			Name:        "content",
+			Type:        "string",
+			Description: "The content to write to the file. Overwrites any existing content!",
+			Required:    true,
+		},
+	},
+	Impl: func(t *api.ToolSpec, args map[string]interface{}) (string, error) {
+		tmp, ok := args["path"]
+		if !ok {
+			return "", fmt.Errorf("Path parameter to write_file was not included.")
+		}
+		path, ok := tmp.(string)
+		if !ok {
+			return "", fmt.Errorf("Invalid path in function arguments: %v", tmp)
+		}
+		tmp, ok = args["content"]
+		if !ok {
+			return "", fmt.Errorf("Content parameter to write_file was not included.")
+		}
+		content, ok := tmp.(string)
+		if !ok {
+			return "", fmt.Errorf("Invalid content in function arguments: %v", tmp)
+		}
+		result := writeFile(path, content)
+		ret, err := result.ToJson()
+		if err != nil {
+			return "", fmt.Errorf("Could not serialize result: %v", err)
+		}
+		return ret, nil
+	},
+}
+
+func writeFile(path string, content string) api.CallResult {
+	ok, reason := toolutil.IsPathWithinCWD(path)
+	if !ok {
+		return api.CallResult{Message: reason}
+	}
+	err := os.WriteFile(path, []byte(content), 0644)
+	if err != nil {
+		return api.CallResult{Message: fmt.Sprintf("Could not write to path: %s", err.Error())}
+	}
+	return api.CallResult{}
+}