editor: gestures work on touch — pinch zooms, a moving finger pans

The stage pointerdown bailed out whenever _markup was set, so in the plan
editor no pointer was ever tracked: no pinch, no pan — on a phone the plan
could not be zoomed or moved at all (owner's report). But drawing is
CLICK-based, so the two coexist: a finger that moves pans (and suppresses
the synthesized click so the release feeds no tool), two fingers pinch, a
clean tap still draws. Pointers that start on labels, handles, markers or
buttons stay out — those run their own drags. The tool preview keeps
following the tracked finger.

New smoke: smoke_editor_gestures (pinch in plan mode, pan without drawing,
tap still draws). Inventory: 140 / 51 / 43 / 66.

docs/TESTING.md

@@ -239,6 +239,9 @@ Run the *core flows* (marked ★ below) in each environment at least once per mi
       on the plan after a reload. Same for each tap action and each fill mode
       [auto: backend test_every_display_mode_the_editor_offers_is_accepted and
       neighbours, test_a_marker_showing_its_value_can_be_saved]
+- [ ] Editor gestures on touch (dev): in the plan editor on a phone, pinch
+      zooms and a moving finger pans; releasing after a gesture does not draw
+      a point, a clean tap still does [auto: smoke_editor_gestures]
 - [ ] Legacy geometry parity (v1.50.4, HP-1503-01): a store with a zero
       viewport and a negative rect renders identically sane in BOTH cards —
       full canvas fallback, normalised rectangle [auto: smoke_legacy_geometry]