graph: the minimap is clickable, and stops swallowing clicks

Click it to jump the view to that part of the graph, drag to scrub. If the
point you clicked is over a block the cursor lands in it, so the keyboard
carries on from where you pointed instead of snapping back.

This also fixes a real bug rather than only adding a feature. The minimap
FLOATS over the canvas -- it is pinned to the viewport, not drawn into the
graph -- so a click on it was being translated into canvas coordinates and
dropping the cursor into whatever block happened to lie underneath. It has to
be hit-tested before the canvas, which is what on_click now does.

_minimap_rect() is the one source of truth for where it is: the renderer and
the hit-test both take the position from it, so the two-column inset that
keeps it clear of the ScrollView's scrollbar can't drift between them.

1 files changed, 8 insertions, 0 deletions

diff --git a/docs/GRAPH_VIEW.md b/docs/GRAPH_VIEW.md
index ccddfe7..6bbcf83 100644
--- a/docs/GRAPH_VIEW.md
+++ b/docs/GRAPH_VIEW.md
@@ -37,6 +37,7 @@ extra work.
 | `x` `n` `y` `;` | xrefs / rename / retype / comment, exactly as in the listing |
 | `Tab` | leave for the pseudocode of the block you're on |
 | mouse | drag to pan, click to place the cursor, double-click to follow |
+| minimap | click to jump the view there, drag to scrub |
 
 Graph mode is **sticky**: following a call from the graph lands in the callee's
 graph rather than dumping you back in the listing.
@@ -109,6 +110,13 @@ per block). On `main` (87 blocks) that is a 1378×518 canvas down to 545×289.
 The **minimap** (`m`) is a coarse occupancy grid of the whole graph with the
 viewport marked, drawn top-right and inset two columns — a `ScrollView` paints
 its scrollbar over the last column, which otherwise eats the minimap's border.
+Clicking it jumps the view to that part of the graph (and lands the cursor on a
+block if one is there, so the keyboard carries on from where you pointed);
+dragging scrubs. Because it floats over the canvas rather than living in it,
+`on_click` has to test the minimap's hit-box **before** translating the click
+into canvas coordinates — otherwise a click on the overview reads as a click on
+whatever block happens to lie underneath it. `_minimap_rect()` is the single
+source of truth for both the drawing and the hit-test.
 
 ## Limits