[compiler] More flexible/helpful lazy ref initialization (facebook#34449)

Two small QoL improvements inspired by feedback:
* `if (ref.current === undefined) { ref.current = ... }` is now allowed.
* `if (!ref.current) { ref.current = ... }` is still disallowed, but we
emit an extra hint suggesting the `if (!ref.current == null)` pattern.

I was on the fence about the latter. We got feedback asking to allow `if
(!ref.current)` but if your ref stores a boolean value then this would
allow reading the ref in render. The unary form is also less precise in
general due to sketchy truthiness conversions. I figured a hint is a
good compromise.

---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34449).
* __->__ facebook#34449
* facebook#34424

DiffTrain build for [bd9e6e0](facebook@bd9e6e0)

Author: pull[bot]

compiled/eslint-plugin-react-hooks/index.js

@@ -1 +1 @@
-b2cff474722953ac6090898850025e41431276e4
+bd9e6e0bed6aed479940b1cf891dde82ab224028

compiled/facebook-www/REVISION

@@ -1 +1 @@
-b2cff474722953ac6090898850025e41431276e4
+bd9e6e0bed6aed479940b1cf891dde82ab224028

compiled/facebook-www/REVISION_TRANSFORMS

@@ -1418,7 +1418,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.2.0-www-classic-b2cff474-20250909";
+    exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-dev.classic.js

@@ -1418,7 +1418,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.2.0-www-modern-b2cff474-20250909";
+    exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-dev.modern.js

@@ -600,4 +600,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-classic-b2cff474-20250909";
+exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";

compiled/facebook-www/React-prod.classic.js

@@ -600,4 +600,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-modern-b2cff474-20250909";
+exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";

compiled/facebook-www/React-prod.modern.js

@@ -604,7 +604,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-classic-b2cff474-20250909";
+exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-profiling.classic.js

@@ -604,7 +604,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-modern-b2cff474-20250909";
+exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-profiling.modern.js

@@ -19708,10 +19708,10 @@ __DEV__ &&
     (function () {
       var internals = {
         bundleType: 1,
-        version: "19.2.0-www-classic-b2cff474-20250909",
+        version: "19.2.0-www-classic-bd9e6e0b-20250910",
         rendererPackageName: "react-art",
         currentDispatcherRef: ReactSharedInternals,
-        reconcilerVersion: "19.2.0-www-classic-b2cff474-20250909"
+        reconcilerVersion: "19.2.0-www-classic-bd9e6e0b-20250910"
       };
       internals.overrideHookState = overrideHookState;
       internals.overrideHookStateDeletePath = overrideHookStateDeletePath;
@@ -19745,7 +19745,7 @@ __DEV__ &&
     exports.Shape = Shape;
     exports.Surface = Surface;
     exports.Text = Text;
-    exports.version = "19.2.0-www-classic-b2cff474-20250909";
+    exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&