docs(readme): scope ns-only bare-visibility claim to values/functions [stdlib B attempt-7]

Phase B tightened bare VALUE/FUNCTION visibility through a namespaced-only
import (isNameVisible/isCImportVisible -> 'not visible'). Bare TYPE names
from such an import still resolve today; type-name visibility tightens in a
later resolver phase. Correct the README so it no longer claims all bare
names from a namespaced import error.

readme.md

@@ -399,10 +399,13 @@ function in the caller's module (or in its single flat import that provides it).
 A bare call to a name that two or more flat imports both provide is ambiguous and
 is rejected; qualify it with a namespaced import (`m :: #import …; m.fn()`).
 
-A **namespaced** import only binds its alias: the module's names are reachable
-solely as `m.name`. A bare reference to one of those names errors with `'name'
-is not visible; #import the module that declares it` — bare-name visibility joins
-over flat (`#import "…"`) imports only, never over a namespaced alias.
+A **namespaced** import only binds its alias: reach the module's members as
+`m.name`. A bare reference to a **value or function** from a namespaced-only
+import errors with `'name' is not visible; #import the module that declares it` —
+bare-name visibility for values and functions joins over flat (`#import "…"`)
+imports only, never over a namespaced alias. (Bare **type** names from a
+namespaced-only import still resolve today; tightening type-name visibility is a
+later resolver phase.)
 
 ### Implicit Context