Add CLAUDE.md with changelog upkeep reminder

1-unit gridlines up to 10, 2-unit up to 20, 5-unit beyond — previously
anything above 10 was squeezed into five segments.

CLAUDE.md

@@ -0,0 +1,11 @@
+# puppy-tracker — notes for Claude
+
+- **Every user-visible change must add an entry to `src/changelog.json`**
+  (newest first, `{ "date": "YYYY-MM-DD", "text": "..." }`). The update banner
+  shows users the entries their new version adds compared to the build they're
+  running, so a missing entry means the change ships silently. Internal-only
+  changes (refactors, server plumbing) don't need one.
+- Commit messages: no Claude attribution / Co-Authored-By lines.
+- Run locally: `nix develop -c sh -c 'cd server && go run . -static ../src -data /tmp/puppy.db -invite-code letmein'`
+- Architecture details are in `README.md` (offline-first PWA, LWW sync with
+  tombstones, per-user data scoping).

src/app.js

@@ -838,19 +838,20 @@
   }
 
   // Pick a chart Y maximum and tick count so every tick label is a clean
-  // whole number (avoids 0, 0, 1, 1, 2 from rounding fractional steps).
+  // whole number (avoids 0, 0, 1, 1, 2 from rounding fractional steps):
+  // 1-unit gridlines up to 10, 2-unit up to 20, 5-unit beyond.
   function niceAxis(rawMax) {
     if (!(rawMax > 0)) return { yMax: 1, steps: 1 };
-    if (rawMax <= 4) {
+    if (rawMax <= 10) {
       const m = Math.ceil(rawMax);
       return { yMax: m, steps: m };
     }
-    if (rawMax <= 10) {
+    if (rawMax <= 20) {
       const m = Math.ceil(rawMax / 2) * 2;
       return { yMax: m, steps: m / 2 };
     }
     const m = Math.ceil(rawMax / 5) * 5;
-    return { yMax: m, steps: 5 };
+    return { yMax: m, steps: m / 5 };
   }
 
   // Sleep-specific axis: always 2-hour granularity, capped at 24h/day,

src/changelog.json

@@ -1,4 +1,5 @@
 [
+  { "date": "2026-07-12", "text": "Finer-grained y-axis on the daily counts chart" },
   { "date": "2026-07-12", "text": "The update banner now lists what changed in the new version" },
   { "date": "2026-07-12", "text": "Fixed adding an exercise on iPhone: stale app updates, and the keyboard's Go key discarding the input" },
   { "date": "2026-07-12", "text": "Training: define exercises with how-to reminders, log sessions in one tap, and follow a 14-day consistency view" }