Import upstream CPython branch '3.14'

Summary:
Python `3.14.0rc1+` (`3.14`) was **published** on 2025-08-07 16:06:09+00:00.

# Commit Info

Base: (`3.14.0rc1+`) - `43d8f527c9997bcbf9341b96feba572aed373b1a` (commit date: 2025-08-06 15:39:52+00:00)
Imported: (`3.14.0rc1+`) - `3.14` (commit date: 2025-08-07 16:06:09+00:00)

# Patches

```
00-patch-patchlevel
01-enable-github-ci
02-trampoline-forward-eval-hook
```

Reviewed By: itamaro

Differential Revision: D79884996

fbshipit-source-id: 6ce05de1976a0ef9c2f759c69ed31270c14201f3

Author: generatedunixname1734921407115435

Doc/whatsnew/3.14.rst

@@ -1697,7 +1697,7 @@ math
 ----
 
 * Added more detailed error messages for domain errors in the module.
-  (Contributed by by Charlie Zhao and Sergey B Kirpichev in :gh:`101410`.)
+  (Contributed by Charlie Zhao and Sergey B Kirpichev in :gh:`101410`.)
 
 
 mimetypes
@@ -3034,7 +3034,6 @@ Porting to Python 3.14
   * ``_PyLong_IsPositive()``: :c:func:`PyLong_IsPositive`
   * ``_PyLong_IsZero()``: :c:func:`PyLong_IsZero`
   * ``_PyLong_Sign()``: :c:func:`PyLong_GetSign`
-  * ``_PyMutex_IsLocked()`` : :c:func:`PyMutex_IsLocked`
   * ``_PyUnicodeWriter_Dealloc()``: :c:func:`PyUnicodeWriter_Discard`
   * ``_PyUnicodeWriter_Finish()``: :c:func:`PyUnicodeWriter_Finish`
   * ``_PyUnicodeWriter_Init()``: use :c:func:`PyUnicodeWriter_Create`
@@ -3048,6 +3047,7 @@ Porting to Python 3.14
   * ``_Py_GetConfig()``: :c:func:`PyConfig_Get` and :c:func:`PyConfig_GetInt`
   * ``_Py_HashBytes()``: :c:func:`Py_HashBuffer`
   * ``_Py_fopen_obj()``: :c:func:`Py_fopen`
+  * ``PyMutex_IsLocked()`` : :c:func:`PyMutex_IsLocked`
 
   The `pythoncapi-compat project`_ can be used to get most of these new
   functions on Python 3.13 and older.

Modules/_zstd/decompressor.c

@@ -157,10 +157,7 @@ _zstd_load_impl(ZstdDecompressor *self, ZstdDict *zd,
                                        zd->dict_len);
     }
     else {
-        /* Impossible code path */
-        PyErr_SetString(PyExc_SystemError,
-                        "load_d_dict() impossible code path");
-        return -1;
+        Py_UNREACHABLE();
     }
 
     /* Check error */