The PR visa validity is calculated from the date of your medical exam, not the submission date. This is also explicitly stated in the Information Letter you received.
Medical date: November 15, 2025
PR visa will be valid until: approximately November 15, 2026
You cannot redo the Medical to Extend the Deadline
You also cannot request a December 2026 Expiry
Solution is Soft Landing-
Fly to Canada before November 23, 2026
Get your PR activated at the port of entry
Fly back to India for your ceremony and time with your spouse
Move to Canada together whenever you're both ready after that.
Correct me if I am wrong guys!