docs(skills): web selectors are exact, native ones are substrings

skills/sanderling-spec-review/SKILL.md

@@ -86,12 +86,20 @@ function of that string can separate them.
 **Match whole keys, not endings or substrings.** `endsWith` attribution judges an
 older account named `Emergency Fund` when the user typed `Fund`.
 
-Selector matching has the same trap and it is easy to miss which keys carry it.
+Selector matching has the same trap on Android and iOS, and it is easy to miss
-`id`, `text`, `desc` and `descPrefix` resolve by their own rules, so `{id: "Sub"}`
+which keys carry it. `id`, `desc` and `descPrefix` resolve by rules of their own
-correctly matches nothing. Every other key, `testTag` included, falls through to a
+(exact or `:id/`-suffixed, exact or comma-prefixed, starts-with), so
-substring compare, so `{testTag: "Sub"}` matches `AddAccountSubmit`. That is not a
+`{id: "Sub"}` correctly matches nothing. Every other key, `text` and `testTag`
-match, it is a coincidence, and a property built on it judges whichever element
+included, falls through to a substring compare, so `{testTag: "Sub"}` matches
-happens to contain the fragment.
+`AddAccountSubmit`. That is not a match, it is a coincidence, and a property
+built on it judges whichever element happens to contain the fragment.
+
+The web path does not share the rule, which is its own trap. `web-runtime.ts`
+compiles an object selector to CSS, and every key becomes an exact attribute
+match (`descPrefix` alone becomes a `^=` prefix). So the loose selector that
+resolved on Android resolves to nothing on web, and every property over it goes
+vacuously true rather than red. Reviewing a cross-platform spec means checking
+that each selector is exact enough for native and literal enough for web.
 
 **Drop the carrier when the screen changes.** A value carried across a route
 change is a value read from a screen that is no longer there.