feat(ux): visual improvements for list tree, graph, and show commands

bd list --tree:
- Use actual parent-child dependencies instead of dotted ID hierarchy
- Treat epic dependencies as parent-child relationships
- Sort children by priority (P0 first)
- Fix tree display in daemon mode with read-only store access

bd graph:
- Add --all flag to show dependency graph of all open issues
- Add --compact flag for tree-style rendering (reduces 44+ lines to 13)
- Fix "needs:N" cognitive noise by using semantic colors
- Add blocks:N indicator with semantic red coloring

bd show:
- Tufte-aligned header with status icon, priority, and type badges
- Add glamour markdown rendering with auto light/dark mode detection
- Cap markdown line width at 100 chars for readability
- Mute entire row for closed dependencies (work done, no attention needed)

Design system:
- Add shared status icons (○ ◐ ● ✓ ❄) with semantic colors
- Implement priority colors: P0 red, P1 orange, P2 muted gold, P3-P4 neutral
- Add TrueColor profile for distinct hex color rendering
- Type badges for epic (purple) and bug (red)

Design principles:
- Semantic colors only for actionable items
- Closed items fade (muted gray)
- Icons > text labels for better scanability

Co-Authored-By: SageOx <ox@sageox.ai>

cmd/bd/show_test.go

@@ -55,8 +55,8 @@ func TestShow_ExternalRef(t *testing.T) {
 	}
 
 	out := string(showOut)
-	if !strings.Contains(out, "External Ref:") {
-		t.Errorf("expected 'External Ref:' in output, got: %s", out)
+	if !strings.Contains(out, "External:") {
+		t.Errorf("expected 'External:' in output, got: %s", out)
 	}
 	if !strings.Contains(out, "https://example.com/spec.md") {
 		t.Errorf("expected external ref URL in output, got: %s", out)
@@ -108,7 +108,7 @@ func TestShow_NoExternalRef(t *testing.T) {
 	}
 
 	out := string(showOut)
-	if strings.Contains(out, "External Ref:") {
-		t.Errorf("expected no 'External Ref:' line for issue without external ref, got: %s", out)
+	if strings.Contains(out, "External:") {
+		t.Errorf("expected no 'External:' line for issue without external ref, got: %s", out)
 	}
 }