Grinder and Saw hopper blocks replace the Refiner and Stone cutter in the menu (t4)

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.
 
+## 2026-10-24: t4: Grinder and Saw hopper blocks (Claude Code, Codex)
+
+- New block pieces `grinder`/`saw` (`BP_GRIND`/`BP_SAW`, materials `GRINDER`/`SAWB`, NMAT 97).
+  `procBlocksTick` (`src/sim/processors.js`) works the row above each stack top and passes the
+  result down the stack (`procFeed`), reusing `REFINE` and `CUT_PER_BRICK`; per-block state in
+  `procState`, rebuilt on place/remove/load. Refiner and Stone cutter are `hidden`; their ticks are
+  unchanged. Texture in `render/world.js`, hover text in `info.js`, Machines tab, notebook.
+- Codex hit its output limit before finishing the tests; I fixed the test setup (a leftover brick
+  blocked the outlet), kept the old machine icons, stopped "blocked" flickering on idle ticks,
+  and added the play.py Machines-tab and drag-a-row checks.
+- Tests: t_stone all pass, play.py 243 pass; t_smooth's half-resolution check fails inside
+  run_all at load ~9 and passes alone (known flake). Screenshots `shots/t4-hoppers{,-smooth}.png`.
+
 ## 2026-10-24: t25: air streaks for the Pneumatic nozzle (Claude Code, Codex)
 
 - `drawAirStreaks` in `src/ui/previews.js`: 12 teal streaks spiral into the ring while sucking, 10