Autoconnect: Filter out secondary composite ports from autoconnect

[DonLakeFlyer]

• Fix for Deal with multiple composite ports on same device #12893
• These changes should bring the basically code back to how 4.4 worked
• The secondary ports from a composite device are not made available to autoconnect
• The list of ports available to manual connections is the full un-filtered list. This differs from 4.4 which filtered the manual connect list as well.
• Fixed SerialLink to not pop PermissionError errors on autoconnect links

So far I've tested Mac and Windows for correct behavior on:

• Eating PermissionError's
• USB cable pull and reconnect. Note: On Windows, same as before, usb cable pull doesn't automatically close link,. You need to disconnect manually.
• Autoconnect to a composite device like Cube Orange running Ardupilot works

This can still cause failures on autoconnect to composite devices line Cube Orange. But it is basically the same failures that occurred with 4.4. Linux seems to be the OS which causes the most grief. In those cases you will need to turn off Autoconnect and manual connect to the right port.

[DonLakeFlyer]

@HTRamsey Can you give Linux and Android a try with this?

[Copilot]

Pull Request Overview

This PR restores 4.4–style autoconnect behavior by filtering out secondary composite USB ports and suppressing permission errors during autoconnect.

• Adjust SerialLink to skip emitting permission errors when auto-connect is enabled
• Add _filterCompositePorts in LinkManager to drop non-MAVLink interfaces on composite devices
• Update LinkManager headers and invoke filtering before establishing serial autoconnect links

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/Comms/SerialLink.cc	Only emit errors on autoconnect when not a permission error; always disconnect port on failure
src/Comms/LinkManager.h	Declared _filterCompositePorts helper
src/Comms/LinkManager.cc	Implemented filtering logic for composite ports and applied it to the autoconnect port list

Comments suppressed due to low confidence (1)

src/Comms/SerialLink.cc:206

• This unguarded call will always disconnect the port, even during autoconnect. Reintroduce a check (e.g. if (!_serialConfig->isAutoConnect())) to prevent disconnecting when auto-connect is active, matching the comment’s intent.

_onPortDisconnected();

[Copilot]

The local variable list is declared but never used. Remove this dead code to improve clarity and avoid confusion.

Suggested change

QList<QGCSerialPortInfo> list;

[HTRamsey]

Linux is good, will try Android tonight