guide: read-only guided manual-rotation layer (links + worklist + TUI)

Advances the guided-rotation goal without rotating anything.

- internal/links: offline change-password URL generation — curated per-service
  table + RFC 8615 /.well-known/change-password + parent-domain fallback; derives
  a web host from a credential (git/netrc "user @ host", docker registry, aws)
- internal/worklist: secrets-free rotation worklist (source, identity, auto/manual,
  link) + Markdown renderer
- internal/tui: Bubble Tea walk-through (one credential per screen, open link,
  mark done/skip, progress) — READ-ONLY, enters/stores no secret
- cmd: `incredigo worklist` (offline, stdout/--out) and `incredigo guide` (TUI)
- tests: link derivation, worklist build/markdown + no-secret-column, TUI
  navigation/done/quit/view

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/worklist/worklist_test.go

@@ -0,0 +1,55 @@
+package worklist
+
+import (
+	"strings"
+	"testing"
+
+	"incredigo/internal/discover"
+)
+
+func TestBuildAndMarkdown(t *testing.T) {
+	creds := []discover.Credential{
+		{Source: "git", Identity: "alice @ github.com", Kind: discover.KindToken},
+		{Source: "ssh", Identity: "id_ed25519", Kind: discover.KindPrivateKey},
+		{Source: "docker", Identity: "ghcr.io", Kind: discover.KindPassword},
+	}
+	items := Build(creds)
+	if len(items) != 3 {
+		t.Fatalf("got %d items, want 3", len(items))
+	}
+	// No drivers are registered yet, so everything is manual.
+	for _, it := range items {
+		if !it.Manual() {
+			t.Errorf("item %q unexpectedly has driver %q", it.Credential.Identity, it.Driver)
+		}
+	}
+	// github link is curated; ssh has no web page.
+	if items[0].Link.URL != "https://github.com/settings/tokens" {
+		t.Errorf("git link = %q", items[0].Link.URL)
+	}
+	if items[1].Link.URL != "" {
+		t.Errorf("ssh should have no link, got %q", items[1].Link.URL)
+	}
+
+	md := Markdown(items)
+	for _, want := range []string{
+		"# incredigo rotation worklist",
+		"3 credential(s)",
+		"https://github.com/settings/tokens",
+		"alice @ github.com",
+		"— (no web page)", // ssh row
+	} {
+		if !strings.Contains(md, want) {
+			t.Errorf("markdown missing %q\n---\n%s", want, md)
+		}
+	}
+}
+
+func TestMarkdownHasNoSecrets(t *testing.T) {
+	// Identities are pre-redacted; assert the renderer never invents a secret column.
+	items := Build([]discover.Credential{{Source: "aws", Identity: "default / AKIA***"}})
+	md := Markdown(items)
+	if strings.Contains(strings.ToLower(md), "password |") && strings.Contains(md, "secret value") {
+		t.Error("worklist must not contain a secret-value column")
+	}
+}