refactor: tighten DDD boundaries on the Feed aggregate

Address five modeling tensions in one pass:

- Encapsulation: the Feed aggregate no longer exposes raw config/metadata
  (a shallow Readonly still leaked mutable arrays). It now offers
  intention-revealing accessors that return copies, plus
  toConfigSnapshot/toMetadataSnapshot for the repository and summary() for
  the global registry.
- feeds:list consistency: FeedRepository.save/saveConfig upsert the registry
  entry from feed.summary(), so services no longer mirror title/description/
  expiry by hand (the old add/updateInList footgun is gone).
- domain/feed.ts: drop the dead applySenderPolicy, internalise resolveExpiresAt
  and trimToByteBudget into the aggregate; feed.ts keeps only the shared
  isExpired predicate used by the read-model routes.
- Single edit path: remove editDetails; edit(patch, deps) is the sole config
  mutation, with a systematic expired guard. Renaming an expired feed now 403s.
- FeedId flows through the application and infrastructure signatures;
  fromTrusted/parse happen once at the edge, .value only at the serialisation
  boundaries (urls, feed-generator, feed-keys, logs, JSON).

347 tests green, tsc clean, Worker bundle builds.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/application/feed-service.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect } from "vitest";
 import { createMockEnv } from "../test/setup";
 import { createFeedRecord, editFeed } from "./feed-service";
 import { getCounters } from "./stats";
+import { FeedId } from "../domain/value-objects/feed-id";
 import type { Env } from "../types";
 
 const mkEnv = (overrides: Partial<Env> = {}) =>
@@ -59,7 +60,9 @@ describe("editFeed — TTL policy", () => {
     const { feedId } = await createFeedRecord(env, { ...baseInput });
 
     const before = Date.now();
-    const result = await editFeed(env, feedId, { title: "renamed" });
+    const result = await editFeed(env, FeedId.fromTrusted(feedId), {
+      title: "renamed",
+    });
 
     expect(result.status).toBe("ok");
     if (result.status === "ok") {
@@ -75,7 +78,9 @@ describe("editFeed — TTL policy", () => {
       lifetimeHours: 5,
     });
 
-    const result = await editFeed(env, feedId, { title: "x" });
+    const result = await editFeed(env, FeedId.fromTrusted(feedId), {
+      title: "x",
+    });
 
     expect(result.status).toBe("ok");
     if (result.status === "ok") {