[eslint-plugin-react-hooks] Include cycle-entry segment in cyclic set

[thomasbuilds]

countPathsFromStart / countPathsToEnd in RulesOfHooks populate a cyclic set of code-path segments so that hooks inside loops can be reported as "may be executed more than once". When a cycle is detected, the code slices the pathList starting at indexOf(segment.id) + 1 — which excludes the repeated segment itself (the cycle-entry / loop-header segment) from the cyclic set.

As a result, a hook that lives directly in the test expression of a while or for loop is not reported, even though it is called on every iteration:

function Component() {
  while (useHook()) { /* ... */ }   // previously not reported
}

function Component() {
  for (; useHook(); ) { /* ... */ } // previously not reported
}

The do { … } while (useHook()) case happened to be reported, but only because of a separate isInsideDoWhileLoop fallback check on the hook node — there was no equivalent for plain while / for, so the bug was invisible there.

The fix slices from the repeated segment itself (indexOf(segment.id) instead of + 1), so every segment participating in the cycle — including the cycle head — is recorded. The change is applied symmetrically to both countPathsFromStart and countPathsToEnd.

How did you test this change?

• Added two new invalid cases to ESLintRulesOfHooks-test.js asserting loopError('useHookInsideLoop') for:

  • while (useHookInsideLoop()) { foo(); }
  • for (; useHookInsideLoop(); ) { foo(); }

  Both cases fail on main (no error reported) and pass with the fix.

• Reproduced the underlying off-by-one with a standalone simulation of the cycle-detection logic over the CFG shape ESLint produces for while (useHook()) { … } (segments: start → test → body → test, test → end):

  OLD slice(indexOf + 1):  cyclic = [ 'body' ]
  NEW slice(indexOf):      cyclic = [ 'test', 'body' ]
  

  The old behavior drops the test segment, which is exactly where the hook in the condition lives — matching the observed false negative.

• Existing tests (including the do { … } while (useHook()) case, and loop-body cases like while (a) { useHook1(); … }) are unaffected: their reported hooks sit in non-header segments that were already captured by the old slice.

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