bpo-29917: DOC: Remove link from PyMethodDef (#890) - #895

window-ml PYTHON_DIALECT.md python#895, replacing 2026-10-15's "restriction is a property of
the entry": a CO_RESTRICTED frame entered while no run is active (not restricted, not
lifted) raises NotInDialect, so a function a cell defined runs nowhere the gate does
not. The check is a tier-1 op at RESUME (_RESTRICTED_ENTRY, in RESUME and
INSTRUMENTED_RESUME), which every route into such code passes: a call, a C library
calling it back from host code, exec() of its code, and a generator's or coroutine's
resumption. RESUME_CHECK deopts on CO_RESTRICTED code and _QUICKEN_RESUME leaves it
unquickened, so a specializing build takes the same check.

The text names the function as the cell wrote it and says what to do: "f() was
defined in a cell that ran inside the read-only dialect, unasked, and runs only
there; define it again in this cell to call it here".

Tests (OutsideRunTest): each route, a nested function, the name without the wrapper's
"_user.<locals>.", and host code untouched; two tests that pinned the old rule now
assert the refusal. Mutation: without the op in RESUME, 9 of 145 fail.

Cost, native arm64 build, 9 interleaved runs, median of best-of-5: 2M calls
95.7 -> 97.0 ms (+0.6 ns/call, x1.013); 2M generator resumptions 64.1 -> 63.2 ms
(x0.986). Both within the runs' spread (90-98 and 95-100 ms; 63-67 and 62-65 ms).

Co-Authored-By: Claude Opus 5.5 <[email protected]>