fix(ci): install root and shared node_modules for the evolution benchmark (#2575)

* fix(ci): install root and shared node_modules for the evolution benchmark

The first real workflow_dispatch of the skill-evolution loop failed at task
binding: capture_task_dependency_binding aborted with

  SandboxError: sandbox_copy path is unavailable: node_modules: No such
  file or directory

The benchmark tasks sandbox-copy node_modules from three locations
(tasks.scenarios.yaml) — the monorepo root, gitnexus-shared, and gitnexus —
mirroring a full dev checkout. The install step only ran `npm ci` in
gitnexus/, so the root and gitnexus-shared node_modules never existed and
the loop died before any agent ran. Install all three (root, then build
gitnexus-shared, then build gitnexus), matching the per-package install in
ci-tests.yml plus the root deps the tasks require.

A new contract test pins all three installs so this fails in CI rather than
on the next real run — the same guard the workflow's other two P1 fixes got.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Va5uu9Ar3e45QZ5xFsG4AZ

* fix(ci): only add the missing root install; the subpackage steps already exist

The initial fix redundantly rebuilt gitnexus-shared and gitnexus inside the
gitnexus step — but the workflow already builds both in their own dedicated
steps. Only the monorepo root node_modules was missing. Add a single
"Install monorepo root dependencies" step and leave the two subpackage
build steps untouched, so the benchmark's root sandbox_copy resolves without
double-building.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Va5uu9Ar3e45QZ5xFsG4AZ

---------

Co-authored-by: Gergo Magyar <gergomagyar@icloud.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/gitnexus-skill-evolution.yml

@@ -151,6 +151,17 @@ jobs:
           test "$("${canary_runtime}/node_modules/@anthropic-ai/claude-code-linux-x64/claude" --version)" = \
             '2.1.214 (Claude Code)'
 
+      - name: Install monorepo root dependencies
+        run: |
+          set -euo pipefail
+          # The benchmark's task bindings sandbox-copy node_modules from the
+          # monorepo root as well as gitnexus-shared and gitnexus (see the
+          # sandbox_copy entries in tasks.scenarios.yaml). The two steps below
+          # install the subpackage trees; the root tree needs its own install
+          # or capture_task_dependency_binding aborts at task binding on the
+          # missing root node_modules.
+          npm ci
+
       - name: Build pinned shared runtime
         run: |
           set -euo pipefail

gitnexus/test/unit/skill-evolution-workflow.test.ts

@@ -59,6 +59,20 @@ describe('gitnexus skill-evolution workflow contract', () => {
     expect(provision).toContain('${HOME}/GitNexus');
   });
 
+  it('installs node_modules for the monorepo root, gitnexus-shared, and gitnexus', () => {
+    // The benchmark sandbox-copies node_modules from all three (tasks.scenarios.yaml).
+    // The root tree was absent on the first real run because only the two subpackage
+    // steps ran, so capture_task_dependency_binding aborted at task binding.
+    const rootStep = evolveJob?.steps?.find(
+      ({ name }) => name === 'Install monorepo root dependencies',
+    );
+    expect(rootStep).toBeDefined();
+    expect(rootStep).not.toHaveProperty('working-directory'); // installs at the repo root
+    expect(String(rootStep?.run)).toContain('npm ci');
+    expect(stepRun('Build pinned shared runtime')).toContain('npm ci');
+    expect(stepRun('Install and build pinned GitNexus runtime')).toContain('npm ci');
+  });
+
   it('names the promotion branch with the run attempt for re-run recovery', () => {
     const openPr = stepRun('Open the promotion PR');
     expect(openPr).toContain('${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}');