fix(vm): reserve jump-table entry 0 for try/finally fallthrough

[tkshsbcue]

The jump table emitted at the end of a try/finally block uses the finally_throw_index register to dispatch to a break/continue/return that was pending when control transferred into the finally. The index register is initialised to 0 and only updated by HandleFinally, so 0 represents "no jump record was selected — fall through past the table".

#4852 made JumpTable index its address array directly and dropped the explicit default address. The same PR also removed the +1 offset that HandleFinally used to apply to its index, so the initial value 0 now collides with the first registered jump record. Any return, break, or continue syntactically present (but not executed) inside a try block whose finally runs is then taken as soon as the finally completes, even though control should fall through to the code after the try statement.

A minimal reproducer (which silently breaks React 19's dispatchSetStateInternal):

function g(x) {
    try { if (x) return -1; } catch (e) {} finally {}
    return 42;
}
g(0); // returned `undefined`, should be `42`

Restore the +1 offset in HandleFinally and size the emitted jump table at N + 1 entries: entry 0 is patched to point past all of the jump-record handlers, and entries 1..=N continue to dispatch to the registered records. A jump emitted right after the table skips the record handlers in the fallthrough case so that the new entry 0 target is only reachable through the table.
Fixes #5369 as well!

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,125	53,125	0
Passed	51,071	51,071	0
Ignored	1,482	1,482	0
Failed	572	572	0
Panics	0	0	0
Conformance	96.13%	96.13%	0.00%

Tested main commit: 8f5ef6542d641fd22320e51234e914b59e623717
Tested PR commit: 1fdef75378315be5058ad638d12444b84dc2077e
Compare commits: 8f5ef65...1fdef75

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.04%. Comparing base (6ddc2b4) to head (1fdef75).
⚠️ Report is 967 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5381       +/-   ##
===========================================
+ Coverage   47.24%   60.04%   +12.80%     
===========================================
  Files         476      566       +90     
  Lines       46892    63027    +16135     
===========================================
+ Hits        22154    37846    +15692     
- Misses      24738    25181      +443     

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