feat: Phase 2 — chat templates, reasoning parser, collapsible TUI, mouse support

- internal/llama/template.go: ChatML/Llama3 template engine with stop tokens
- internal/agent/reasoning.go: parse <think>/<reasoning> tags from LLM output
- companion/promptbuilder.go: output structured BuildResult, add date/time context
- agent/agent.go: wire templates + reasoning split into message loop
- storage: add reasoning TEXT column to messages table + migration
- channel/tui.go: collapsible reasoning (tab toggle), mouse scroll, polished dimmed style
- config: CHAT_TEMPLATE env var (chatml|llama3|none)
- plan.md: mark Phase 2 complete, add themes TODO

internal/llama/client.go

@@ -15,12 +15,13 @@ type Client struct {
 }
 
 type CompletionRequest struct {
-	Prompt      string  `json:"prompt"`
-	Temperature float64 `json:"temperature"`
-	TopP        float64 `json:"top_p"`
-	MaxTokens   int     `json:"n_predict"`
-	Stream      bool    `json:"stream"`
-	CachePrompt bool    `json:"cache_prompt"`
+	Prompt      string   `json:"prompt"`
+	Temperature float64  `json:"temperature"`
+	TopP        float64  `json:"top_p"`
+	MaxTokens   int      `json:"n_predict"`
+	Stop        []string `json:"stop,omitempty"`
+	Stream      bool     `json:"stream"`
+	CachePrompt bool     `json:"cache_prompt"`
 }
 
 type CompletionResponse struct {

internal/llama/template.go

@@ -0,0 +1,71 @@
+package llama
+
+import (
+	"fmt"
+	"strings"
+
+	"git.db123.ir/db123/divacode/pkg/types"
+)
+
+type TemplateEngine struct {
+	format string
+}
+
+func NewTemplateEngine(format string) *TemplateEngine {
+	return &TemplateEngine{format: format}
+}
+
+func (te *TemplateEngine) Build(segments []types.PromptSegment) string {
+	switch te.format {
+	case "chatml":
+		return te.buildChatML(segments)
+	case "llama3":
+		return te.buildLlama3(segments)
+	default:
+		return te.buildRaw(segments)
+	}
+}
+
+func (te *TemplateEngine) StopTokens() []string {
+	switch te.format {
+	case "chatml":
+		return []string{"<|im_end|>"}
+	case "llama3":
+		return []string{"<|eot_id|>"}
+	default:
+		return nil
+	}
+}
+
+func (te *TemplateEngine) buildChatML(segments []types.PromptSegment) string {
+	var b strings.Builder
+	for _, seg := range segments {
+		b.WriteString(fmt.Sprintf("<|im_start|>%s\n%s<|im_end|>\n", seg.Type, seg.Content))
+	}
+	b.WriteString("<|im_start|>assistant\n")
+	return b.String()
+}
+
+func (te *TemplateEngine) buildLlama3(segments []types.PromptSegment) string {
+	var b strings.Builder
+	b.WriteString("<|begin_of_text|>")
+	for _, seg := range segments {
+		b.WriteString(fmt.Sprintf("<|start_header_id|>%s<|end_header_id|>\n\n%s<|eot_id|>", seg.Type, seg.Content))
+	}
+	b.WriteString("<|start_header_id|>assistant<|end_header_id|>\n\n")
+	return b.String()
+}
+
+func (te *TemplateEngine) buildRaw(segments []types.PromptSegment) string {
+	var b strings.Builder
+	for _, seg := range segments {
+		switch seg.Type {
+		case types.SegSystem:
+			b.WriteString("[System]\n" + seg.Content + "\n\n")
+		case types.SegUser:
+			b.WriteString("User: " + seg.Content + "\n")
+		}
+	}
+	b.WriteString("You:")
+	return b.String()
+}