Document Sketcher tangent orientation fix

[er1c-cartman]

Summary:
Adds a FreeCAD 1.2 release-note entry for FreeCAD/FreeCAD#29015.

Related bounty or issue:
Refs #94.

What changed:

• Documented that line-circle and line-arc tangent constraints now use computed orientation to keep geometry on the intended side during solving.
• Kept the update limited to the root Release_notes_1.2 page.

Validation:

• git diff --check -- wiki/Release_notes_1.2.wikitext
• Confirmed the upstream pull/29015 link appears once.
• Confirmed translate tag counts remain balanced.

Notes:

• Translation files were intentionally not modified.
• This is a focused release-note addition and does not claim the broader Sketcher documentation issue is complete.