Tap-target check expects a pin button per WAN host row (closes #46)

The viewport harness's tap-target check required at least 10 visible
pin buttons while 26 render, so pin buttons missing from up to 16 rows
went unnoticed. It now expects one per WAN host row. The host row count
the harness gathers, which the app-rendered check also reads, counts
only the WAN host rows, since the local host rows have no pin button.
Each control's minimum is now worked out from the gathered facts.

TODO.md's harness entry no longer says every check guards itself: the
overflow, viewport-edge and clipped-text checks rely on app-rendered.

Model: opus-5-5

TODO.md

@@ -23,6 +23,11 @@ latest run passes.
 
 # Completed Steps
 
+- 2026-10-03: the tap-target check in `make frontend-viewport-test` expects one
+  visible pin button per WAN host row (issue #46), where it expected at least 10
+  of the 26, so pin buttons missing from only some rows now fail it. The host
+  row count the harness gathers, which the `app-rendered` check also reads, now
+  counts only the WAN host rows: the local host rows have no pin button
 - 2026-10-03: `backend/script/lint` says what went wrong with its
   `.golangci.yml` check (issue #34). On a hash mismatch it says to compare the
   file with the org standard: if they differ, restore the org standard; if they
@@ -211,9 +216,11 @@ latest run passes.
 - 2026-08-09: automated responsive-layout harness
   (`make frontend-viewport-test`): digest-pinned headless Chrome driven over CDP
   against the built `dist/`, viewport widths derived from the breakpoints in
-  `src/styles.css` ([#13](https://git.eeqj.de/sneak/netwatch/issues/13)). Every
-  check carries a presence guard so none of them can pass against a page it is
-  not actually measuring. Found two real layout defects, filed as
+  `src/styles.css` ([#13](https://git.eeqj.de/sneak/netwatch/issues/13)). The
+  tap-target and host-row checks each fail when they measured nothing; the
+  overflow, viewport-edge and clipped-text checks have no such guard of their
+  own and rely on the `app-rendered` check, which fails the run when the app did
+  not render. Found two real layout defects, filed as
   [#42](https://git.eeqj.de/sneak/netwatch/issues/42) and
   [#43](https://git.eeqj.de/sneak/netwatch/issues/43)
 - 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints, Makefile

test/viewport/README.md

@@ -49,10 +49,11 @@ sizes straddling the breakpoint for the rotation case.
   excluded: it is a design choice, not breakage.
 - **tap-targets-44px** — every interactive control is at least 44x44 CSS px on
   touch viewports, _and_ each selector in the control list matched at least the
-  number of visible elements it declares. The second half is what stops the
-  check passing vacuously: with size alone, a renamed class would take its
-  controls out of the measured set and the check would report "all 0 controls
-  are at least 44x44" and pass. See below.
+  number of visible elements it declares: one of each single control, and one
+  pin button per WAN host row. The second half is what stops the check passing
+  vacuously: with size alone, a renamed class would take its controls out of the
+  measured set and the check would report "all 0 controls are at least 44x44"
+  and pass. See below.
 - **host-rows-stacked / host-rows-side-by-side** — the rows genuinely reflow.
   Computed `flex-direction` _and_ the actual geometry are checked, and in the
   narrow layout the info block and the sparkline must each occupy essentially

test/viewport/checks.js

@@ -15,7 +15,8 @@ export const MIN_TAP_TARGET_PX = 44;
 
 // The controls named in the definition of done, plus the pause button.
 // Each carries the smallest number of *visible* instances the page has to
-// contain for the tap-target oracle to be measuring anything at all.
+// contain, worked out from the facts gathered from that page, for the
+// tap-target oracle to be measuring every control it should.
 //
 // Without those floors the check is inert: `undersized` is empty both when
 // every control is large enough and when the selectors have gone stale and
@@ -24,13 +25,12 @@ export const MIN_TAP_TARGET_PX = 44;
 // for all three singleton controls vanishing at once — so the floor is per
 // selector, and one stale selector out of four fails the check.
 export const INTERACTIVE_CONTROLS = [
-    { selector: "#pause-btn", minCount: 1 },
-    { selector: "#interval-select", minCount: 1 },
-    // One per pinnable host row. `app-rendered` already requires at least
-    // 10 host rows, so a count below that means the pin buttons stopped
-    // being rendered per row rather than that there were fewer hosts.
-    { selector: ".pin-btn", minCount: 10 },
-    { selector: "#debug-toggle", minCount: 1 },
+    { selector: "#pause-btn", minCount: () => 1 },
+    { selector: "#interval-select", minCount: () => 1 },
+    // One per WAN host row, so pin buttons missing from even one row fail
+    // the check rather than only a drop below some fixed number.
+    { selector: ".pin-btn", minCount: (facts) => facts.rowCount },
+    { selector: "#debug-toggle", minCount: () => 1 },
 ];
 
 export const INTERACTIVE_SELECTORS = INTERACTIVE_CONTROLS.map(
@@ -106,7 +106,7 @@ export function evaluateChecks(facts, viewport, probes) {
     check(
         "app-rendered",
         facts.rowCount >= 10 && facts.numericLatencies >= 5,
-        `${facts.rowCount} host rows, ${facts.numericLatencies} showing a numeric latency`,
+        `${facts.rowCount} WAN host rows, ${facts.numericLatencies} showing a numeric latency`,
     );
 
     const viewportWidth = Math.min(facts.innerWidth, facts.documentClientWidth);
@@ -162,7 +162,8 @@ export function evaluateChecks(facts, viewport, probes) {
             seen.set(target.selector, (seen.get(target.selector) ?? 0) + 1);
         }
         const missing = INTERACTIVE_CONTROLS.filter(
-            (control) => (seen.get(control.selector) ?? 0) < control.minCount,
+            (control) =>
+                (seen.get(control.selector) ?? 0) < control.minCount(facts),
         );
 
         const undersized = facts.tapTargets.filter(
@@ -184,11 +185,11 @@ export function evaluateChecks(facts, viewport, probes) {
         const detail = [];
         if (missing.length > 0) {
             detail.push(
-                "oracle is not measuring the page: " +
+                "oracle is not measuring every control: " +
                     summarise(
                         missing,
                         (c) =>
-                            `${c.selector} matched ${seen.get(c.selector) ?? 0} visible element(s), expected at least ${c.minCount}`,
+                            `${c.selector} matched ${seen.get(c.selector) ?? 0} visible element(s), expected at least ${c.minCount(facts)}`,
                         4,
                     ),
             );

test/viewport/facts.js

@@ -173,7 +173,9 @@ export function collectLayoutFacts(options) {
         clipped,
         tapTargets,
         rows,
-        rowCount: document.querySelectorAll(".host-row").length,
+        // WAN host rows only: each has a pin button, and the tap-target
+        // check expects one per row. The local host rows have none.
+        rowCount: document.querySelectorAll("#wan-hosts .host-row").length,
         numericLatencies: Array.from(
             document.querySelectorAll(".latency-value"),
         ).filter((el) => /\d/.test(el.textContent)).length,