One rule for a piece's direction variant: remove pieceV (t81)

docs/PROJECT_MAP.md

@@ -671,6 +671,7 @@ The frame loop and boot.
 - `test/t_nozzle.js`: Blowing aims within the nozzle's reach, with room for the brush and settling.
 - `test/t_perf.js`: Profiling fixtures start in the same state after previous scenes and warm-up ticks.
 - `test/t_physics.js`: Sand and other powders, molten metal and gases: heaps, sorting, sinking, setting, rising and fading. Water has its own suite (t_water.js). Tall worlds keep geothermal heat out of the way.
+- `test/t_piece_variants.js`: The build plan and direct variant queries share one direction/material rule.
 - `test/t_pile_collapse.js`: Tall loose faces release together; supported heaps stop moving, including when revisited.
 - `test/t_pipes.js`: Pipes, pumps and outlets move liquids; the Grinder grinds waste rock for trace ore.
 - `test/t_racks.js`: Rack intake, FIFO storage, gate, removal and saved-state validation.

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.
 
+## 2026-10-29: t81 shared piece direction variants (Codex)
+
+- `pieceV` accepts a direction and resolved code; `dragPlan` calls it for previews and
+  placement. Default queries keep the selected direction. No world generation changes.
+- Files: src/ui/selection.js, test/t_piece_variants.js, docs/PROJECT_MAP.md, tasks/t81*.
+- New checks: 29 failures before, all 72 pass after. All 41 headless suites pass;
+  all 40 existing suite outputs match before/after, ignoring timing lines (empty
+  /tmp/t81-determinism.diff). Pixel test/play.py passes with no console errors; inspected
+  shots/t81-play/04-{blocks,diagonal-screws}.png. Sandbox WebGPU was unavailable;
+  host GPU rerun passed. Nothing left open; t81 ready for owner review.
+
 ## 2026-10-29: t96 rebuilt: lakes are bowls filled to their spill level (Claude)
 
 - Owner: the round-4 bank was a flat, unnatural ramp; fix lake generation properly instead of