Diagonal screw tubes, laid by a 45° drag (t35)

- Tubes run in eight directions: a drag at about 45° lays a diagonal run, R cycles all eight.
- Diagonal runs carry grains at the straight rate (120 grains/s), join straight tubes and belts,
  keep grains in at the corners, pass water, and carry bars level.
- New part ids 11-14 (saved ids are never renumbered); tube checks use an IS_TUBE table.
- New test/t_diag_tubes.js (85 checks).

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

docs/agent-log.md

@@ -4,6 +4,17 @@ 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.
 
+## 2026-10-25: t35: diagonal screw tubes (Claude Code, Codex)
+
+- Parts `P_TUR`..`P_TUL` (11-14), `TUBE_PARTS`, and an `IS_TUBE` table replacing every
+  `P_TU..P_TR` range check (`src/sim/material-tables.js` and its users); tube variants 4-7;
+  diagonal drags for tubes; grains in `src/sim/conveyors.js`/`cells.js`, bars in `items.js`;
+  both looks, previews, hover, copy/paste, undo, blueprints, saves.
+- `test/t_diag_tubes.js` (85 checks): 120 grains/s straight, up and down over ten blocks; joins,
+  no spills, water passes, bars both ways, controls, persistence. Existing suites unchanged and
+  passing; seeds unchanged. `run_all.py --browser` ALL PASSED. Screenshots
+  `shots/t35-diagonal-*.png`, scene `tools/scenes/t35-diagonal.js`.
+
 ## 2026-10-25: t36: sloped walls and diagonal wall lines (Claude Code, Codex)
 
 - `BP_SLOPE_BL`..`BP_SLOPE_TR` (15-18) in `src/sim/pieces.js` (`isSlope`, `isWall`, `slopeCell`,