refactor(domain): slim detectConfirmation contract

Return the ranked links directly (string[] | null) instead of an unused
{score, links} wrapper, and drop the redundant hasKeyword helper in favor
of matchesAny(_, KEYWORDS). No behavior change.

src/application/email-processor.ts

@@ -187,7 +187,7 @@ async function storeEmail(
     return false; // signal: skipped (not stored)
   }
 
-  const confirmation = detectConfirmation({
+  const confirmationLinks = detectConfirmation({
     subject: input.subject,
     text: htmlToText(input.content),
     links: extractLinks(input.content),
@@ -229,7 +229,9 @@ async function storeEmail(
     ...(inlineIds.length > 0 ? { inlineAttachmentIds: inlineIds } : {}),
     ...(messageId ? { messageId } : {}),
     dedupHash,
-    ...(confirmation ? { confirmation: { links: confirmation.links } } : {}),
+    ...(confirmationLinks
+      ? { confirmation: { links: confirmationLinks } }
+      : {}),
   };
 
   // Track the latest sender's domain (feed icon) and capture the RFC 8058

src/domain/confirmation.test.ts

@@ -15,9 +15,7 @@ describe("detectConfirmation", () => {
       ],
     });
     expect(result).not.toBeNull();
-    expect(result!.links[0]).toBe(
+    expect(result![0]).toBe("https://news.example.com/confirm?token=abc123");
-      "https://news.example.com/confirm?token=abc123",
-    );
   });
 
   it("detects a French confirmation email (accent-insensitive)", () => {
@@ -32,7 +30,7 @@ describe("detectConfirmation", () => {
       ],
     });
     expect(result).not.toBeNull();
-    expect(result!.links[0]).toBe("https://lettre.example.fr/valider/xyz");
+    expect(result![0]).toBe("https://lettre.example.fr/valider/xyz");
   });
 
   it("returns null for a normal newsletter with only an unsubscribe link", () => {
@@ -69,7 +67,7 @@ describe("detectConfirmation", () => {
       ],
     });
     expect(result).not.toBeNull();
-    expect(result!.links).not.toContain("https://x.example/unsubscribe");
+    expect(result!).not.toContain("https://x.example/unsubscribe");
   });
 
   it("ranks the strongest candidate first and caps at three links", () => {
@@ -85,8 +83,8 @@ describe("detectConfirmation", () => {
       ],
     });
     expect(result).not.toBeNull();
-    expect(result!.links.length).toBeLessThanOrEqual(3);
+    expect(result!.length).toBeLessThanOrEqual(3);
-    expect(result!.links[0]).toBe("https://x.example/confirm?token=2");
+    expect(result![0]).toBe("https://x.example/confirm?token=2");
   });
 
   it("ignores non-http(s) links", () => {

src/domain/confirmation.ts

@@ -15,11 +15,6 @@ export interface DetectConfirmationInput {
   links: { href: string; text: string }[];
 }
 
-export interface ConfirmationResult {
-  score: number;
-  links: string[];
-}
-
 // Confirmation-positive stems, already normalized (lowercased, diacritics stripped).
 // EN / FR / DE / ES — extend here to add a language.
 const KEYWORDS = [
@@ -79,10 +74,6 @@ function matchesAny(haystack: string, needles: string[]): boolean {
   return needles.some((n) => haystack.includes(n));
 }
 
-function hasKeyword(haystack: string): boolean {
-  return KEYWORDS.some((kw) => haystack.includes(kw));
-}
-
 function linkScore(href: string, text: string): number {
   const h = normalize(href);
   const t = normalize(text);
@@ -101,7 +92,7 @@ function stripNegatives(text: string): string {
 
 export function detectConfirmation(
   input: DetectConfirmationInput,
-): ConfirmationResult | null {
+): string[] | null {
   const candidates = input.links
     .filter((l) => isHttp(l.href))
     .map((l) => ({ href: l.href.trim(), score: linkScore(l.href, l.text) }))
@@ -113,12 +104,11 @@ export function detectConfirmation(
   const subject = stripNegatives(normalize(input.subject));
   const text = stripNegatives(normalize(input.text));
 
-  const subjectScore = hasKeyword(subject) ? 2 : 0;
+  const subjectScore = matchesAny(subject, KEYWORDS) ? 2 : 0;
-  const bodyScore = hasKeyword(text) ? 1 : 0;
+  const bodyScore = matchesAny(text, KEYWORDS) ? 1 : 0;
   const bestLinkScore = candidates[0].score;
 
-  const score = subjectScore + bodyScore + bestLinkScore;
+  if (subjectScore + bodyScore + bestLinkScore < THRESHOLD) return null;
-  if (score < THRESHOLD) return null;
 
-  return { score, links: candidates.slice(0, 3).map((c) => c.href) };
+  return candidates.slice(0, 3).map((c) => c.href);
 }