docs(i18n): name the oracle's blindness to attribute-borne copy (#2208)

Co-authored-by: Kandev Agent <agent@kandev.dev>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/i18n.md

@@ -403,15 +403,37 @@ through `t()` — that is the acceptance check for a migrated screen, and the on
 one that sees the guard's blind spots. Interpolation placeholders and `<n>` tag
 markers are preserved by the generator.
 
-Two qualifications, both below: an **interpolated API or network payload** stays
-English by design, so it is not a miss even though it renders unaccented; and
-plain English is not a *complete* signal, because a payload inside a translated
-frame renders accented and reads as done.
+One thing it shows you is **not** a miss: an interpolated API or network payload
+stays English by design, so it renders unaccented and is still correct. See
+[the interpolated-value limit](#and-it-is-weakest-at-an-interpolated-value).
 
-It has one blind spot of its own: **module-scope `t()`**. That copy *is*
-translated, just frozen at the boot locale, so it renders accented under pseudo
-and looks correct while never responding to a switch. `check-module-scope-t.mjs`
-is what catches it.
+Three things it cannot show you at all — the second and third are detailed below:
+
+1. **Module-scope `t()`.** That copy *is* translated, just frozen at the boot
+   locale, so it renders accented and looks correct while never responding to a
+   switch. `check-module-scope-t.mjs` is what catches it.
+2. **Copy that never becomes a text node** — an attribute string leaves no trace
+   on screen at all.
+3. **An un-migrated value interpolated into a migrated frame** — it renders
+   inside accented copy and reads as done.
+
+### It cannot see copy that is not a text node
+
+`findUnlocalizedText` in `e2e/tests/i18n/pseudo-coverage.spec.ts` walks
+`NodeFilter.SHOW_TEXT`, and a human looking at the screen is no different:
+**copy carried in an attribute — `aria-label`, `aria-description`, `title`,
+`placeholder`, `alt` — renders nothing visible and leaves no trace under
+pseudo.** The Settings → System → Storage review demonstrated it by reverting an
+`aria-label` to an English template literal; nothing failed.
+
+The guard is the primary defence here, not the oracle: those five attributes are
+in `jsx-attributes.include`, so on an allowlisted path the lint rule does flag
+them. The consequence is that for attribute copy there is **no second check** — on
+a path not yet allowlisted, or for a fragment the `words.exclude` patterns skip,
+nothing downstream catches it. The copy only screen-reader users receive is
+therefore the copy with the weakest safety net. Read attribute props by eye when
+you migrate, and prefer a `t()` call over a template literal in them so the value
+stays greppable.
 
 ### …and it is weakest at an interpolated value