Your leak area is pretty much identical to mine, and I will share my solution (new cowl).
It took me almost a month of searching through this forum, other Toyota forums, and also constant spray of water & going through carwash to test the new remedies.
Of course, I did clean out the sunroof drain first with a proper soft cleaning tool... no issue here.
Checked the sunroof gasket and roof rack mounting points... even AC drain? no issue!
Local windshield shop came by and tested the seal... again no issue.
Finally, removed the old cowl and applied new gasket according to the possible fix found on other thread... reduced the water leakage but not completely eliminated.
FYI, you really have to remove that plastic cover under the passenger compartment with carpet padding on it.
(That carpet padding will absorb the water that entered into the cabin and also reduce the actual leakage onto the floor & difficult to trace exact source)
I suggest you to actually cover up the HVAC inlet completely with a plastic tape or something to find out if it's indeed cowl related leak.
Go through the carwash and see any water coming down onto the passenger floor.
You might get away with a new gasket like others did... however, on my case, new Cowl from Toyota dealer fixed the issue completely.
Replacing with new gasket from Lowes wasn't adequate in my case.
Yes, I believe it's a design flaw but I'm not the engineer to judge...
Luckily, I found the issue right away and no sign of corrosion or weird smell.
I believe the dealer replaced the windshield prior to my purchase and messed up the cowl when they putting it back.
YMMV....
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