Attach images to posts and return the Telegram message id

The adapter response now carries telegram_message_id and a t.me/c link.
compose visual resolves a post's image: own visual_url, else the entry's
rendered portrait, else hold an entry with only a visual prompt, else the
HelixForge main image. send-post.sh resolves before touching credentials,
requires an image on public posts and runs the adapter with ATTACH_VISUAL.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 5457@bnt-lap001
Assistant-Session: 792bf84a-3783-4f5d-a811-cded61dd2012

internal/compose/visual.go

@@ -0,0 +1,130 @@
+package compose
+
+import (
+	"errors"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+// VisualKind says where a post's image comes from. Public posts carry an
+// image; the order of preference is the post's own visual_url (set by the
+// caller), then the entry's rendered portrait, then a render of the entry's
+// visual prompt, and only for a post with no prompt at all the campaign's
+// main image.
+type VisualKind string
+
+const (
+	VisualPortrait    VisualKind = "portrait"
+	VisualNeedsRender VisualKind = "needs-render"
+	VisualFallback    VisualKind = "fallback"
+)
+
+// Visual is the resolved image for one post. For VisualNeedsRender, URL is
+// empty, Prompt is the entry's brief and Target the file the hall expects the
+// render at (empty if the entry names none). Such a post is not published
+// with the fallback: the entry asked for its own portrait.
+type Visual struct {
+	Kind   VisualKind `json:"kind"`
+	URL    string     `json:"visual_url,omitempty"`
+	Path   string     `json:"path,omitempty"`
+	Prompt string     `json:"prompt,omitempty"`
+	Target string     `json:"target,omitempty"`
+}
+
+var (
+	htmlComment  = regexp.MustCompile(`(?s)<!--.*?-->`)
+	markdownImg  = regexp.MustCompile(`!\[[^\]]*\]\(([^)\s]+)\)`)
+	visualTarget = regexp.MustCompile(`visuals/[A-Za-z0-9._-]+\.(?:jpe?g|png)`)
+	// A bare file name in backticks, as draft seats name their intended render.
+	namedTarget = regexp.MustCompile("`([A-Za-z0-9._-]+\\.(?:jpe?g|png))`")
+)
+
+// ResolveVisual picks the image for a post written from entryMarkdown, which
+// is empty for a post that has no source entry (an outlet post). Portrait
+// paths are returned relative to the hall repository root ("visuals/x.png")
+// and joined onto hallRawBase; the caller checks that the file exists.
+func ResolveVisual(entryMarkdown, hallRawBase, fallbackURL string) (Visual, error) {
+	if entryMarkdown != "" {
+		visible := htmlComment.ReplaceAllString(entryMarkdown, "")
+		for _, m := range markdownImg.FindAllStringSubmatch(visible, -1) {
+			rel := portraitPath(m[1])
+			if rel == "" {
+				continue
+			}
+			u, err := joinURL(hallRawBase, rel)
+			if err != nil {
+				return Visual{}, err
+			}
+			return Visual{Kind: VisualPortrait, URL: u, Path: rel}, nil
+		}
+		if body, ok := section(entryMarkdown, "Visual prompt"); ok {
+			if prompt := promptText(body); prompt != "" {
+				return Visual{
+					Kind:   VisualNeedsRender,
+					Prompt: prompt,
+					Target: renderTarget(entryMarkdown),
+				}, nil
+			}
+		}
+	}
+	if fallbackURL == "" {
+		return Visual{}, errors.New("no portrait or visual prompt, and no fallback image configured")
+	}
+	return Visual{Kind: VisualFallback, URL: fallbackURL}, nil
+}
+
+// renderTarget is where the hall expects the entry's portrait: a
+// visuals/<file> path anywhere in the entry, else a backticked image file name.
+func renderTarget(markdown string) string {
+	if t := visualTarget.FindString(markdown); t != "" {
+		return t
+	}
+	if m := namedTarget.FindStringSubmatch(markdown); m != nil {
+		return "visuals/" + m[1]
+	}
+	return ""
+}
+
+// portraitPath reduces an entry's image link ("../visuals/x.png") to its
+// path in the hall repository, or "" for a link that is not a hall visual.
+func portraitPath(link string) string {
+	if strings.Contains(link, "://") {
+		return ""
+	}
+	i := strings.Index(link, "visuals/")
+	if i < 0 {
+		return ""
+	}
+	return link[i:]
+}
+
+// promptText is the brief inside a Visual prompt section: its quoted lines
+// when it has any, without the quote markers; otherwise the section minus
+// image lines and italic status notes.
+func promptText(body string) string {
+	var quoted, plain []string
+	for _, line := range strings.Split(htmlComment.ReplaceAllString(body, ""), "\n") {
+		t := strings.TrimSpace(line)
+		switch {
+		case strings.HasPrefix(t, ">"):
+			quoted = append(quoted, strings.TrimSpace(strings.TrimPrefix(t, ">")))
+		case t == "", markdownImg.MatchString(t), strings.HasPrefix(t, "_"):
+		default:
+			plain = append(plain, t)
+		}
+	}
+	if len(quoted) > 0 {
+		return strings.TrimSpace(strings.Join(quoted, " "))
+	}
+	return strings.TrimSpace(strings.Join(plain, " "))
+}
+
+func joinURL(base, rel string) (string, error) {
+	u, err := url.Parse(base)
+	if err != nil || u.Host == "" || (u.Scheme != "http" && u.Scheme != "https") {
+		return "", errors.New("hall raw base must be an absolute http(s) URL")
+	}
+	u.Path = strings.TrimRight(u.Path, "/") + "/" + rel
+	return u.String(), nil
+}