Record following-feed hardening merge in briefing and backlog

By specifier.

specifier-prompt.md

@@ -368,5 +368,5 @@ At the end of each session, update this file:
 - Note the current `master` HEAD commit.
 - State the next feature to work on.
 
-Current `master` HEAD: `62d6297` (task `following-feed` — P6.6 Following Feed — merged from the pipeline and verified: client build/test/lint and DB test/lint all pass).
+Current `master` HEAD: `4422372` (merge of the architect's second-pass hardening of the Following feed — P6.6 — verified: client build/test/lint and DB test/lint all pass).
-Next action: **pick the next feature** from the backlog. Send money (P5.1) was skipped by user decision (no clear use case). Remaining candidates: P5.2–5.5 (MIP-0009 token exchange), P6.1 Repost, P6.2 Ranked feed, P6.3 Notifications, P6.5 Tags/hashtags.
+Next action: **P6.3 Notifications** — the Gherkin spec is drafted at `psf-memo-client/specs/notifications.feature` (8 scenarios, parsed clean, DRY-checked) and is awaiting user approval before handoff to the coder. After approval, commit it (`By specifier.`), invent the stable task name `notifications`, and send the `git_handoff` to the coder. Send money (P5.1) was skipped by user decision (no clear use case). Remaining candidates after notifications: P5.2–5.5 (MIP-0009 token exchange), P6.1 Repost, P6.2 Ranked feed, P6.5 Tags/hashtags.

specs/feature-backlog.md

@@ -213,7 +213,7 @@ Polls require a new data model and rendering. The indexer has no handler yet.
 
 ## Suggested next spec
 
-**Following feed (P6.6)** — ✅ shipped (task `following-feed`), merged from the pipeline and verified (client build/test/lint, DB test/lint). Following Feed is a read-only aggregation: the viewer sees top-level posts (replies excluded) authored only by profiles they follow, newest first, never their own posts. 
+**Following feed (P6.6)** — ✅ shipped (task `following-feed`), merged from the pipeline and verified (client build/test/lint, DB test/lint). A second-pass hardening merge from the architect (2026-09-02) extracted `parseRequiredString` into `pagination.js` (shared by the addr/room-scoped list use cases) and added client + DB composition-root hardening tests; merged to `master` at `4422372` and re-verified. Following Feed is a read-only aggregation: the viewer sees top-level posts (replies excluded) authored only by profiles they follow, newest first, never their own posts. 
 - `psf-memo-db`: `GET /posts/following/:addr?limit=&offset=` returning `{ posts, pagination }`, joining the follows index (`FollowQuery.listFollowing`) with the posts index (`PostQuery.scanFollowingFeedTxidsAndCount`). Empty following or no posts → empty result set.
 - `psf-memo-client`: a "Following" nav page at `/posts/following` that reads the viewer's wallet address, calls `MemoDb.getFollowingFeed`, and renders posts like the recent feed; shows "You are not following anyone." when following nobody and "No posts from profiles you follow." when followed profiles have no posts.
 - Spec: `psf-memo-client/specs/following-feed.feature`.