Manual directional navigation edges are not preserved

[alice-i-cecile]

Bevy version and features

0.18-dev, post #22124

Problem

#22124 FYI this PR means that the docs stating "respects manual edges (they always take precedence)" is stale and this block of code in the rebuilding graph logic

bevy/crates/bevy_input_focus/src/directional_navigation.rs

Lines 670 to 677 in 3ab5c2c

	// Skip if manual edge already exists (check inline to avoid borrow issues)
	if nav_map
	.get_neighbors(origin.entity)
	.and_then(|neighbors| neighbors.get(octant))
	.is_some()
	{
	continue; // Respect manual override
	}

is meaningless since the entire graph is cleared IIUC.

From Discord by ZymartuGames.

Proposed solution

We can probably mark manual edges and do a partial rebuild? Not sure yet.

We need to avoid regressing #21949 though, so a simple revert is sub-optimal.