Action matrix: nightly shards cut by measured cost, a fresh baseline, and a determinism check (#1256)

* Action matrix: nightly shards cut by measured cost, heavy designs in slices, and a determinism check

The full matrix ran as four fixed quarters of the corpus and two of them hit the 60-minute
job limit. Now action_matrix_shard runs shard k of n (ACTION_MATRIX_SHARD=k/n), planned from
tests/action_matrix/costs.json: designs that take more than five minutes are split into slices,
and the pieces go largest first to the least loaded shard. The nightly runs 12 shards and uploads
each one's outcomes and timings; cargo xtask action-matrix --from DIR --bless records them in the
baseline and costs.json without running the matrix again. action_matrix_determinism runs a sample
twice and lists any action whose outcome changed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* Action matrix: costs measured on runners, 10 shards, determinism on the lighter designs

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* Action matrix: baseline and costs from a full run on main, 16 shards, timeouts listed

The baseline is regenerated from the 10 shards' results of a full run on 01b1b705
(cargo xtask action-matrix --from DIR --bless): 8 new designs, 302 actions that pass now,
names that changed, and 40 actions that passed before and fail now, each listed in #1255
(22 fillets refused since #949, 4 hinge blends since #1101, 9 on the loft cut, 5 single).
costs.json now holds every design's measured time, and the nightly runs 16 shards of about
17 minutes. An action that passes in the baseline and times out is listed but not judged,
and stays passing when blessed: two runs of the same build differed only on 10 actions that
took 50-84 s against the 90 s limit.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* Action matrix: slice heavy designs by a hash of each action's name

Slicing by index gave some slices only fillets on oracle 41 (28 slices, a multiple of the
actions per edge), three times the planned time; two shards ran past their limit.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

---------

Co-authored-by: Claude Opus 5.5 <[email protected]>

xtask/src/main.rs

@@ -35,10 +35,12 @@ commands:
                   replay the reference tests (tests/oracle/*/recipe.json), compare with each
                   case's expected.json and write docs/oracle.md (--cli: a solidcraft-cli
                   already built, instead of cargo run --release)
-  action-matrix [--bless] [--results FILE]
+  action-matrix [--bless] [--results FILE] [--from DIR]
                   try every ordinary action on every face, edge, vertex and body of the design
                   corpus and compare with tests/action_matrix/baseline.json (--bless rewrites it;
-                  --results keeps every outcome with its message). See docs/action-matrix.md
+                  --results keeps every outcome with its message; --from takes the outcomes of the
+                  nightly shards' artifacts in DIR instead of running, and --bless then also
+                  rewrites tests/action_matrix/costs.json). See docs/action-matrix.md
   book [--no-build]
                   generate docs/book's command reference and screenshots, then mdbook build
                   into target/book
@@ -71,7 +73,8 @@ fn main() -> ExitCode {
         Some("i18n") => i18n::run(&root(), &rest),
         Some("oracle") => cmd_oracle(rest.iter().position(|a| *a == "--cli").and_then(|i| rest.get(i + 1)).copied()),
         Some("action-matrix") => {
-            cmd_action_matrix(rest.contains(&"--bless"), rest.iter().position(|a| *a == "--results").and_then(|i| rest.get(i + 1)).copied())
+            let arg = |name: &str| rest.iter().position(|a| *a == name).and_then(|i| rest.get(i + 1)).copied();
+            cmd_action_matrix(rest.contains(&"--bless"), arg("--results"), arg("--from"))
         }
         Some("book") => book::run(&root(), !rest.contains(&"--no-build")),
         Some("licences") => licences::run(&root(), rest.contains(&"--check")),
@@ -128,7 +131,7 @@ pub fn metadata() -> Result<serde_json::Value, String> {
 }
 
 /// The full action matrix (apps/solidcraft-cli/tests/action_matrix.rs), with the ci profile.
-fn cmd_action_matrix(bless: bool, results: Option<&str>) -> Result<(), String> {
+fn cmd_action_matrix(bless: bool, results: Option<&str>, from: Option<&str>) -> Result<(), String> {
     let mut c = cargo();
     c.args([
         "test",
@@ -151,6 +154,10 @@ fn cmd_action_matrix(bless: bool, results: Option<&str>) -> Result<(), String> {
         let p = std::path::absolute(r).map_err(|e| format!("{r}: {e}"))?;
         c.env("ACTION_MATRIX_RESULTS", p);
     }
+    if let Some(d) = from {
+        let p = std::path::absolute(d).map_err(|e| format!("{d}: {e}"))?;
+        c.env("ACTION_MATRIX_MERGE", p);
+    }
     run(c, "cargo test --profile ci -p solidcraft-cli --test action_matrix action_matrix_all")
 }