Fix: uDV skipped initial value if earlier transition suspended (facebook#34376)

Fixes a bug in useDeferredValue's optional `initialValue` argument. In
the regression case, if a new useDeferredValue hook is mounted while an
earlier transition is suspended, the `initialValue` argument of the new
hook was ignored. After the fix, the `initialValue` argument is
correctly rendered during the initial mount, regardless of whether other
transitions were suspended.

The culprit was related to the mechanism we use to track whether a
render is the result of a `useDeferredValue` hook: we assign the
deferred lane a TransitionLane, then entangle that lane with the
DeferredLane bit. During the subsequent render, we check for the
presence of the DeferredLane bit to determine whether to switch to the
final, canonical value.

But because transition lanes can themselves become entangled with other
transitions, the effect is that every entangled transition was being
treated as if it were the result of a `useDeferredValue` hook, causing
us to skip the initial value and go straight to the final one.

The fix I've chosen is to reserve some subset of TransitionLanes to be
used only for deferred work, instead of using entanglement. This is
similar to how retries are already implemented. Originally I tried not
to implement it this way because it means there are now slightly fewer
lanes allocated for regular transitions, but I underestimated how
similar deferred work is to retries; they end up having a lot of the
same requirements. Eventually it may be possible to merge the two
concepts.

DiffTrain build for [3302d1f](facebook@3302d1f)

Author: pull[bot]

compiled/facebook-www/REVISION

@@ -1 +1 @@
-ac3e705a18696168acfcaed39dce0cfaa6be8836
+3302d1f791f3f1cf4e8cf69bee70ce5dab1b8436

compiled/facebook-www/REVISION_TRANSFORMS

@@ -1 +1 @@
-ac3e705a18696168acfcaed39dce0cfaa6be8836
+3302d1f791f3f1cf4e8cf69bee70ce5dab1b8436

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

@@ -1418,7 +1418,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.2.0-www-classic-ac3e705a-20250902";
+    exports.version = "19.2.0-www-classic-3302d1f7-20250903";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

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

@@ -1418,7 +1418,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.2.0-www-modern-ac3e705a-20250902";
+    exports.version = "19.2.0-www-modern-3302d1f7-20250903";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

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-classic-ac3e705a-20250902";
+exports.version = "19.2.0-www-classic-3302d1f7-20250903";

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

@@ -600,4 +600,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-modern-ac3e705a-20250902";
+exports.version = "19.2.0-www-modern-3302d1f7-20250903";

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-classic-ac3e705a-20250902";
+exports.version = "19.2.0-www-classic-3302d1f7-20250903";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

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

@@ -604,7 +604,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.2.0-www-modern-ac3e705a-20250902";
+exports.version = "19.2.0-www-modern-3302d1f7-20250903";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&