[megathread] Accessibility links

A tracking thread for different accessibility queries. These bugs are also tracked internally, and require additional process around resolving in a timely fashion.

### Immediately relevant:

* [x] #13019
* [ ] #13020

### Queries
* [All issues](https://github.com/microsoft/terminal/issues?q=is%3Aissue+is%3Aopen+label%3AHCL-WindowsTerminal)
* [`A11ySev1`](https://github.com/microsoft/terminal/issues?q=is%3Aissue+is%3Aopen+label%3AA11ySev1++label%3AHCL-WindowsTerminal+)''s: These go into the current release milestone
* [`A11ySev2`](https://github.com/microsoft/terminal/issues?q=is%3Aissue+is%3Aopen+label%3AA11ySev2++label%3AHCL-WindowsTerminal+)''s: These go into the current semester
* [`A11ySev3`](https://github.com/microsoft/terminal/issues?q=is%3Aissue+is%3Aopen+label%3AA11ySev3++label%3AHCL-WindowsTerminal+)'s: These go into the current year.
* [`A11yUsable`](https://github.com/microsoft/terminal/issues?q=is%3Aissue+is%3Aopen+label%3AA11yUsable++label%3AHCL-WindowsTerminal+)': These go on the backlog

> #### Triage Guidelines:
>
> Please triage bugs as per below:
>
> * To stay compliant, Triage MAS tagged with “A11yMAS” on priority.
> * Triage MAS bugs in the sequence tagged with A11ySev1, A11ySev2 and A11ySev3
>
>
> #### Criteria to calculate Accessibility compliance grading:
>
> * High impact/A11ySev1 bugs greater than 60 days ​
> * Medium impact/A11ySev2 bugs and exceptions greater than 120 days ​
> * More than 5 medium impact/A11ySev2 bugs and partner dependencies
> * Conformance statements older than a year ​

### Blocked on upstream:

_No Sev2 or higher bugs currently blocked on upstream_

* [x] #11250
- upstream: https://github.com/microsoft/microsoft-ui-xaml/issues/3494
* [x] #11159
- upstream: https://github.com/microsoft/microsoft-ui-xaml/issues/3156
- Closed by just removing all the `RadioButton`s in the SUI, #12833

SV2 Era

* [x] #11155
* [x] #11248
- fixed in #11442
* [x] #8480
- fixed in #12260
* [x] #11251
- fixed in #12259
* [x] #7907
- fixed in #12266
* [x] #11996
- fixed in #12299
* [x] #12052
- fixed in #12097
* [x] [**UPSTREAM**] #12021 blocked on https://github.com/microsoft/microsoft-ui-xaml/issues/1607
- Closed by very manually yeeting focus, #12798

This is a tracking thread rather than a self-contained code task. Start by reviewing the unresolved item #13020 and the linked accessibility issue queries; done would require triaging or resolving individual accessibility bugs, but this issue does not identify a file, test, or single change.

Written by the indexing model from the issue text.