test(#1970): consolidate 61 install-suite regression tests into function suites

Fold 61 issue-named install/codex/runtime regression files into the canonical
test file that owns each subject-under-test, preserving every assertion and its
origin issue number as provenance (block-scoped describe wrappers, zero assertion
loss — 652 subtests conserved 1:1). Routes:

- codex-config.test.cjs        +19 (codex config/toml/hooks/adapter/skill surface)
- install.test.cjs             +18 (node-runner norm, manifest, arg parse, finishInstall)
- install-runtime-artifacts    +13 (per-runtime conversion + emission)
- install-minimal-hooks        +6  (hook-event dialects + guards)
- path-replacement             +2  (opencode absolute pathPrefix)
- install-write-confinement    +2  (pristine dir writes)
- install-regressions          +1  (user-artifact preservation)

Removes 61 tests/ files → 61 fewer CI processes. Regenerates the regression-name
allowlist (271→222), ratchets the file-count allowlist (config 10→9, install 12→9),
and makes 13 relocated allow-test-rule exemptions issue-ref-compliant (ADR-456;
prunes 13 stale allowlist ids). Repoints ADR-0009's moved-test list. lint:ci green.

Part of epic #1969. Closes #1970.

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

scripts/lint-test-file-count.allowlist.json

@@ -16,7 +16,6 @@
         "bug-2943-config-get-context-window-default.test.cjs",
         "bug-321-config-defaults-clone-strategy.test.cjs",
         "bug-3227-config-set-model-overrides.test.cjs",
-        "bug-442-config-dir-equals-in-path.test.cjs",
         "config-field-docs.test.cjs",
         "config-get-default.test.cjs",
         "config-schema.property.test.cjs",
@@ -110,12 +109,12 @@
         "bug-3454-state-dollar-backreference-growth.test.cjs",
         "bug-397-state-preserve-executor-authored.test.cjs",
         "bug-905-state-syncstatefrontmatter-preserve-scalars.test.cjs",
-    "bug-948-state-noop-write-guard.test.cjs",
-    "state-acquirestatelock-non-eexist.test.cjs",
-    "state-prune.test.cjs",
-    "state-rebuild-cli.test.cjs",
-    "state-rebuild.test.cjs",
-    "state.test.cjs"
+        "bug-948-state-noop-write-guard.test.cjs",
+        "state-acquirestatelock-non-eexist.test.cjs",
+        "state-prune.test.cjs",
+        "state-rebuild-cli.test.cjs",
+        "state-rebuild.test.cjs",
+        "state.test.cjs"
       ],
       "issue": "180"
     },
@@ -137,10 +136,7 @@
     },
     "install": {
       "files": [
-        "bug-410-install-defaults-test-mode-guard.test.cjs",
-        "enh-1077-install-hook-events-dialect-drive.test.cjs",
         "enh-1082-install-plan-capstone.test.cjs",
-        "enh-776-install-gemini-hook-events.test.cjs",
         "install-minimal-hooks.test.cjs",
         "install-nested-layout.test.cjs",
         "install-path-detection.test.cjs",