test(#1975): scope GSD_TEST_MODE off in real-install folds; fix ci-test-scope fixture

gsd-test surfaced 21 failures:
- 19: folded real-install suites (bug-1834 .sh hooks, enh-2380 --skills-root, fix-1521
  install stamping, bug-2136 .sh hook version) spawn install.js and assert side effects,
  but their host suites (install-minimal-hooks/install.test/managed-hooks) set
  GSD_TEST_MODE=1 at collection time — the install child inherited it and suppressed
  the writes. Clear GSD_TEST_MODE in each of those blocks (before/after; standalone had
  it unset), so the child performs a real install.
- 2: ci-test-scope A1 used deleted tests/bug-1974-context-exhaustion-record.test.cjs as a
  fixture; scopeFor filters nonexistent paths, so it fell back to ['unit']. Repointed to
  its consolidation destination tests/perf-317-context-monitor-fs.test.cjs (an existing test).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/managed-hooks.test.cjs

@@ -74,6 +74,14 @@ describe('bug #2136: MANAGED_HOOKS must include all shipped hook files', () => {
 {
   const { describe: __foldDescribe } = require('node:test');
   __foldDescribe("folded:bug-2136-sh-hook-version (consolidation epic #1969 B6 #1975)", () => {
+  // Consolidation #1969: this block spawns a REAL install and asserts side effects.
+  // The host suite sets GSD_TEST_MODE=1 at collection time, which the install child
+  // inherits via process.env and which suppresses hook/skill writes. Clear it for
+  // this block's duration (standalone had it unset); restore after.
+  const { before: __gtmBefore, after: __gtmAfter } = require('node:test');
+  let __savedGsdTestMode;
+  __gtmBefore(() => { __savedGsdTestMode = process.env.GSD_TEST_MODE; delete process.env.GSD_TEST_MODE; });
+  __gtmAfter(() => { if (__savedGsdTestMode === undefined) delete process.env.GSD_TEST_MODE; else process.env.GSD_TEST_MODE = __savedGsdTestMode; });
 
 // allow-test-rule: structural-regression-guard (see #2136)
 // The shebang line must be `#!/usr/bin/env bash` (PATH-resolved) rather than