.gitlab-ci.yml: substrate-score job + CLI invocation v8 → substrate

Third refactor-induced defect caught from yesterday's v7+v8 →
substrate rename (`bae5caf` for the package, `209d670` for the
Makefile). Same pattern: a callsite that text-search misses
because the import path doesn't connect through Python.

CI surface (the `v8-score:` GitLab CI job) had two issues:

1. Job name `v8-score:` was a UX surface — operators see it in the
   GitLab MR pipeline UI. Renamed to `substrate-score:` for
   consistency with the package name + the CLI subcommand.
2. Script line called ``.venv/bin/arborist v8 score …``. Would
   have failed on the next manual MR pipeline run with an
   argparse "invalid choice: 'v8'" error.

Comment block (lines 80-90 + 115-125) refreshed to call out the
distinction: ``v8 paper`` (the substrate-paper version, name
preserved per published convention) vs the module location
(``arborist/substrate/fork_score.py`` post-2026-05-10 rename).

Sweep verified: ``grep -rnE "arborist v[0-9]\\b|arborist\\.v[78]\\b"``
across the entire tree returns only intentional historical-note
comments + the placeholder-seed bytestring derivation (which
cannot change without invalidating KAT vectors).

Three loose ends from one refactor:
- 85be5eb: fork_score.py import (Python imports caught by tests)
- 209d670: Makefile bench-fork-score target (would surface on run)
- this:    .gitlab-ci.yml job (would surface on next MR pipeline)

Lesson written across the three commits: text-search-replace on
a CLI rename misses callsites that argparse processes at runtime.
Pre-rename checklist for next time: ``grep -rn "<cli-old-name>"
Makefile .gitlab-ci.yml .github/workflows scripts bench``.

.gitlab-ci.yml

@@ -81,7 +81,7 @@ test:
 # Bench gate — runs the complete Dav1DPrometheus suite (5S + 5T + 5F
 # + 5R = 21 sub-batteries, 462+ deterministic fixtures) on every push.
 # Job fails if any fixture fails. Bench result JSON is stored as a
-# pipeline artifact so the v8-score job (below) can compare branches.
+# pipeline artifact so the substrate-score job (below) can compare branches.
 # Wall-clock ~3-5s on the in-house runner; cheaper than `make test`.
 #
 # Closes the loop from "we have a fitness substrate" (#000021,
@@ -113,17 +113,19 @@ bench-suite:
     expire_in: 30 days
 
 # ----------------------------------------------------------------------
-# v8 ForkScore gate — for merge requests, score the bench delta
-# between this branch and main. ACCEPT or MARGINAL pass; REJECT fails
-# the job. Phase 1 of #000012's selection protocol; the consensus
-# layer (validators, slashing, fork-choice) lives in the v8 paper
-# itself.
+# Substrate ForkScore gate — for merge requests, score the bench
+# delta between this branch and main. ACCEPT or MARGINAL pass;
+# REJECT fails the job. Phase 1 of #000012's selection protocol; the
+# consensus layer (validators, slashing, fork-choice) lives in the
+# Merkle-AGI v8 paper itself (paper version, not module location —
+# the module is at arborist/substrate/fork_score.py per the
+# 2026-05-10 v7+v8 → substrate refactor).
 #
-# This job is `manual` for now — auto-gating waits until the v8 paper
-# pins weight-set defaults for arborist's deployment shape. Operators
-# trigger it on demand from the MR UI.
+# This job is `manual` for now — auto-gating waits until the v8
+# paper pins weight-set defaults for arborist's deployment shape.
+# Operators trigger it on demand from the MR UI.
 # ----------------------------------------------------------------------
-v8-score:
+substrate-score:
   stage: test
   tags:
     - build
@@ -162,7 +164,7 @@ v8-score:
           > /tmp/parent.json || \
         echo '{"schema_version":"bench-result-v1","results":[]}' > /tmp/parent.json
     # Score child vs parent. Exit 1 on REJECT (gates the merge).
-    - .venv/bin/arborist v8 score --parent /tmp/parent.json --child "$CHILD"
+    - .venv/bin/arborist substrate score --parent /tmp/parent.json --child "$CHILD"
 
 # ----------------------------------------------------------------------
 # Optional: crawler extras + crawler-tagged tests. Opt-in via the