Corner placements of screw conveyors stay separate ends (t62 follow-up)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/agent-log.md

@@ -4,6 +4,19 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-27: t62 corner placements stay separate (Claude Code + Codex)
+
+- Owner tried the corner join and found the jog odd; decision (recorded in DESIGN.md): only
+  same-row joins connect. Removed join kinds 5/6 and `straightScrewNext`; `diagonalScrewNext`
+  and `entDiagonalScrewTick` now continue across a corner only into a diagonal running the same
+  way, so a corner straight piece no longer receives grains or bars. Kept the shared geometry
+  file and the smooth-look elbow seam fix.
+- Files: `src/render/diagonal-screws.js`, `src/render/smooth-shaders.js`, `src/sim/conveyors.js`,
+  `src/sim/items.js`, `src/sim/machine-tick.js`, `test/t_diag_screws.js`, `test/t_smooth.py`,
+  `tools/scenes/t62-joins.js`, `docs/PROJECT_MAP.md`, `docs/DESIGN.md`.
+- Tests: `python3 test/run_all.py --browser` all passed; determinism diff changed only the
+  replaced corner checks.
+
 ## 2026-10-27: t62 screw conveyor joins (Claude Code + Codex)
 
 - Straight screws touching a diagonal's end only at the corner now join, in both looks and in