Add agent library

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/agent/system_prompt.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package agent
+
+import (
+	"bytes"
+	"text/template"
+)
+
+type (
+	systemPromptData struct {
+		Instructions string
+		Handoffs     []systemPromptHandoff
+	}
+
+	systemPromptHandoff struct {
+		Name        string
+		Description string
+	}
+)
+
+var systemPromptTmpl = template.Must(template.New("system_prompt").Parse(
+	`{{- .Instructions -}}
+{{- if .Handoffs }}
+
+## Handoffs
+You can transfer the conversation to a more specialized agent when appropriate:
+{{ range .Handoffs -}}
+- {{ .Name }}{{ with .Description }}: {{ . }}{{ end }}
+{{ end -}}
+{{- end -}}
+`))
+
+func buildSystemPrompt(data systemPromptData) string {
+	var buf bytes.Buffer
+	_ = systemPromptTmpl.Execute(&buf, data)
+
+	return buf.String()
+}