chore(changelog): announce the changelog, and make entries a convention

The changelog's own entry names the commit before this one, since a
commit cannot contain its own hash. AGENTS.md now asks every
reader-visible change for an entry, and every multi-commit feature for a
note, so the record keeps up. PRD F18 and the storage and design records
describe what shipped.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/DATA-MODEL.md

@@ -227,6 +227,10 @@ Namespaced, versioned, and small. Nothing here ever goes to the server.
                                 // the reader turned on; routinesAsked the games already
                                 // asked about. Both absent means none — built-ins are
                                 // opt-in for every install. PRD F17.
+                                // changelogSeen is the newest changelog entry id the
+                                // reader dismissed. Absent means unrecorded: first-run
+                                // setup sets it, so absent is an install from before the
+                                // changelog, shown the last 14 days once. PRD F18.
                                 // timelineDayWidth is px per day on the board, stored as the
                                 // measurement rather than a step number and read through
                                 // snapDayWidth — so a value from an older ladder still opens

docs/DESIGN.md

@@ -415,6 +415,13 @@ selected tab fills with `raised` and turns ink; unselected tabs are faint and go
   label, a small numeric field on `ground`, `/ 2,100 points`, and a near-pill Save. Weekly and
   monthly counts sit on their own faint line under the strip's heading, so the reset countdown
   never wraps.
+- **What's new card** (top of the main column, never the rail): the eyebrow, up to five lines of
+  kind (faint, fixed width) · title (muted) · date (faint, hidden on phones), then a near-pill
+  **Got it** and a faint **See all**. Shown once per batch of changes; never modal.
+- **Changelog sheet** (from the footer's *Changelog*, beside *Source code*): the detail sheet's
+  frame. Each release note is a section — date eyebrow, title, summary paragraphs in muted ink, the
+  short entries it covers with commit links, then a faint line of `commits from…to` and spec links.
+  Entries with no note follow under *Other changes*, by month.
 - **Built-in question** (top of the dailies strip, once per game): one line of muted text —
   `Track Zenless Zone Zero's built-in weekly tasks?` — with a near-coloured **Yes** and a faint **No
   thanks** as plain text buttons. Never a card, never a modal; the strip renders for it alone.

docs/PRD.md

@@ -571,6 +571,21 @@ once, in one line, about a game on screen that has them, and a switch per game i
 governs them after. Built-ins are not edited in place; **Make it mine** copies one into the reader's
 own tasks with its ticks and numbers, and hides the original while the copy exists.
 
+**F18 — What changed.**
+The app now says what changed, in two tiers, both tied to git. **Short entries** — one line each,
+tagged New, Fixed, or Games & sources — appear once as *What's new*, above the lists, after a new
+version loads; *Got it* dismisses them. **Release notes** — a few paragraphs per feature or
+milestone, summarised from the history and the design specs — are in the footer's *Changelog*, each
+linked to the commits it covers and the specs it draws on. Data refreshes are not changes in this
+sense; the footer already states the data's age.
+
+- **After the reload, not before.** The update notice (F14) is the old app, which cannot know what
+  the new one brings, so the news waits for the version that carries it. Nothing is fetched.
+- **A new reader is not shown a history.** First-run setup marks them up to date. A reader from
+  before the changelog existed is shown the last two weeks once, so its arrival is announced.
+- **Written for readers, by a person or an agent, at development time** — never generated at
+  runtime (AGENTS.md constraint 2).
+
 ## Out of scope for v1
 
 Accounts and sync; push notifications; in-game resource or pull tracking; native mobile apps (the

docs/superpowers/specs/2026-10-13-changelog-design.md

@@ -2,7 +2,8 @@
 
 **Date:** 2026-10-13
 
-**Status:** approved; spec 3. Independent of specs 1 and 2, and announces them.
+**Status:** implemented 2026-10-13; spec 3. The card and sheet landed together; three same-day
+fix entries for bugs no reader ever saw were left out of the backfill. Independent of specs 1 and 2, and announces them.
 
 ## Request and intended outcome