Engine unification: d3-force replaces forceAtlas2 everywhere

One engine owns the equilibrium: the merge settle and (next commit)
the live drag both run createGraphSimulation — d3-force link springs,
1/d charge, weak centroid gravity — so a drag's rest state IS the
server's rest state. The FA2-era anchor mechanism survives as a
post-tick POSITION-SPACE re-blend (retention 0.85): d3's forceLink is
a Hooke spring (strength*(d-L)*alpha), which overpowers any force-space
anchor at long range — the re-blend is alpha-independent and always
wins as the sim anneals (the 675-unit drift bug). Gravity retuned for
d3's 1/d many-body falloff (bootstrap 0.2 / incremental 0.12: cluster
spacing lands ~400 world units, the FA2-era density). Rim orphans seed
(and anchor) at 1.7x the CONNECTED core's mean radius — a max-span-based
rim fed back on itself and ran the layout away to 6000 units. Replay:
338 positions in 1.6s, old-node shift within a batch 4.8 (FA2: 23).

package-lock.json

@@ -24,6 +24,7 @@
 				"class-variance-authority": "^0.7.1",
 				"clsx": "^2.1.1",
 				"cmdk": "^1.1.1",
+				"d3-force": "^3.0.0",
 				"d3-selection": "^3.0.0",
 				"d3-zoom": "^3.0.0",
 				"embla-carousel-react": "^8.6.0",