feat(tui): add cards view, mode switching, promote picker, and card detail

Stream/cards toggle with 1/2 keys. Cards view with intent filtering
(tab cycles grab/read/fill/all), sort cycling (s key), pinned-first
ordering, and affordance badges. Promote picker (p key) with card type
selection and auto-detection from body content. Detail view renders
card_data per type: checklist steps, template slots, decision fields,
link URLs.

Extracts generateCardData to internal/carddata for reuse across cmd
and tui packages.

internal/carddata/carddata.go

@@ -0,0 +1,102 @@
+package carddata
+
+import (
+	"encoding/json"
+	"regexp"
+	"strings"
+
+	"github.com/lerko/nib/internal/db"
+)
+
+var TemplateSlotRe = regexp.MustCompile(`\$\{(\w+)\}`)
+
+func GenerateCardData(ct db.CardType, body string) *string {
+	var data string
+	switch ct {
+	case db.CardTemplate:
+		matches := TemplateSlotRe.FindAllStringSubmatch(body, -1)
+		type slot struct {
+			Name    string `json:"name"`
+			Default string `json:"default"`
+		}
+		var slots []slot
+		seen := map[string]bool{}
+		for _, m := range matches {
+			name := m[1]
+			if !seen[name] {
+				slots = append(slots, slot{Name: name, Default: ""})
+				seen[name] = true
+			}
+		}
+		if slots == nil {
+			slots = []slot{}
+		}
+		b, _ := json.Marshal(map[string]any{"slots": slots})
+		data = string(b)
+
+	case db.CardChecklist:
+		type step struct {
+			Text string `json:"text"`
+			Done bool   `json:"done"`
+		}
+		var steps []step
+		for _, line := range strings.Split(body, "\n") {
+			line = strings.TrimSpace(line)
+			if strings.HasPrefix(line, "[ ]") || strings.HasPrefix(line, "[x]") {
+				text := strings.TrimSpace(line[3:])
+				done := strings.HasPrefix(line, "[x]")
+				steps = append(steps, step{Text: text, Done: done})
+			}
+		}
+		if steps == nil {
+			steps = []step{{Text: body, Done: false}}
+		}
+		b, _ := json.Marshal(map[string]any{"steps": steps})
+		data = string(b)
+
+	case db.CardDecision:
+		b, _ := json.Marshal(map[string]any{
+			"chose":    "",
+			"why":      "",
+			"rejected": []string{},
+		})
+		data = string(b)
+
+	case db.CardLink:
+		url := ""
+		for _, word := range strings.Fields(body) {
+			if strings.HasPrefix(word, "http://") || strings.HasPrefix(word, "https://") {
+				url = word
+				break
+			}
+		}
+		b, _ := json.Marshal(map[string]any{"url": url})
+		data = string(b)
+
+	default:
+		data = "{}"
+	}
+	return &data
+}
+
+func DetectCardType(body string) *db.CardType {
+	if TemplateSlotRe.MatchString(body) {
+		ct := db.CardTemplate
+		return &ct
+	}
+	if strings.Contains(body, "chose:") || strings.Contains(body, "why:") {
+		ct := db.CardDecision
+		return &ct
+	}
+	if strings.Contains(body, "[ ]") || strings.Contains(body, "[x]") {
+		ct := db.CardChecklist
+		return &ct
+	}
+	for _, word := range strings.Fields(body) {
+		if strings.HasPrefix(word, "http://") || strings.HasPrefix(word, "https://") {
+			ct := db.CardLink
+			return &ct
+		}
+	}
+	return nil
+}