docs(tools): qualify the three remaining mode-dependent only-claims

The `mode: 'code'` qualification landed on the module header and
`isBareIdentifier` but not on the other three sites the same reviews
enumerated. `UNPRINTABLE`'s "only declaration of the tools", the open-object
comment's "only signal that extra keys are accepted", and the docstring
comment's "only description of what a tool does" are each false under
`mode: 'both'`, where the native schemas ship alongside the SDK.

Widen the note's predicate-path sentence past head and last position: a
character added to `XID_Continue` passes `IDENTIFIER`'s trailing quantifier
anywhere after the head, the middle of a name included.

Record the ƛ test's table provenance. U+A7DC and the U+019B mapping to it
both arrive in Unicode 16.0, and the engines floor sits exactly there:
Node 22.19.0 reports Unicode 16.0 (ICU 77.1) and produces the mapping.

packages/core/tools/tests/py-types.spec.ts

@@ -480,6 +480,14 @@ describe('renderToolsSdkPy', () => {
     // an older interpreter's do not. This pins which table produced the name,
     // so a change to the mapping step shows up here rather than only in a
     // downstream Python parse.
+    //
+    // Unlike the other Unicode cases in this file, the table row is recent:
+    // U+A7DC and the U+019B uppercase mapping to it both arrive in Unicode
+    // 16.0 (`DerivedAge.txt`; CPython 3.12.13's 15.0.0 has neither). The
+    // engines floor sits exactly there with no margin — Node 22.19.0 reports
+    // Unicode 16.0 (ICU 77.1) and maps U+019B to U+A7DC, measured — so an
+    // engine below the floor fails here as a renderer regression whose real
+    // cause is the table version.
     const text = renderToolsSdkPy([
       {
         name: 'ƛ',