Finish the wonderland: System told truthfully, in eight tabs instead of ten

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/scripts/panama-settings-sync

@@ -58,6 +58,17 @@ MACHINE_SPECIFIC = {
 # machine where the file exists. Carried, then checked on arrival.
 PATH_VALUED = {"wallpaperPath", "wallpaperSlideshowPaths"}
 
+# A preview is something a person reads before pressing Import. Past a screen or
+# two it stops being read and starts being scrolled, so the list is capped and
+# the count says how many there really are -- the import itself still applies
+# every change, because the cap is about what is shown, not what is done.
+CHANGE_LIMIT = 40
+
+# Long enough for a wallpaper path or a theme name, short enough that no single
+# row can push the rest off the screen. Values are rendered for display here,
+# never re-parsed, so a truncated one costs nothing.
+VALUE_LIMIT = 120
+
 
 class BoundaryError(RuntimeError):
     """A user-visible validation or file failure."""
@@ -158,6 +169,29 @@ def fits(entry: dict, value) -> str:
     return ""
 
 
+def render(value) -> str:
+    """One setting's value as a line of text a person can compare.
+
+    Rendered here rather than in the page because the page would have to know
+    the difference between a JSON setting and a scalar one to do it, and that
+    knowledge already lives in the schema on this side. A value with no entry
+    at all is "not set" rather than "null": the two look identical in JSON and
+    mean quite different things to somebody reading a diff.
+    """
+    if value is None:
+        return "not set"
+    if isinstance(value, bool):
+        return "on" if value else "off"
+    if isinstance(value, (int, float)):
+        return f"{value:g}" if isinstance(value, float) else str(value)
+    if isinstance(value, str):
+        text = value
+    else:
+        text = json.dumps(value, separators=(",", ":"), sort_keys=True)
+    text = " ".join(text.split())
+    return text if len(text) <= VALUE_LIMIT else text[:VALUE_LIMIT - 1] + "…"
+
+
 def exportable() -> tuple[dict, list[dict]]:
     known = schema()
     current = stored()
@@ -248,14 +282,17 @@ def plan(path: str) -> dict:
             continue
         apply[key] = value
         changes.append({"key": key,
-                        "from": current.get(key, None),
-                        "to": value})
+                        "from": render(current.get(key)),
+                        "to": render(value)})
 
     return {
         "path": str(Path(path).expanduser()),
         "exportedFrom": str(bundle.get("exportedFrom", "")),
         "exportedAt": int(bundle.get("exportedAt", 0)),
-        "changes": changes,
+        "changes": changes[:CHANGE_LIMIT],
+        # What the list would have held uncapped, so the page can say "and 12
+        # more" rather than quietly showing forty of fifty-two.
+        "changeCount": len(changes),
         "skipped": skipped,
         "apply": apply,
     }