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>

docs/adr/0009-shell-command-projection-module.md

@@ -52,11 +52,11 @@ These call sites should migrate behind the Shell Command Projection Module:
 
 ### Tests expected to move with the seam
 
-- `tests/bug-2979-hook-absolute-node.test.cjs`
+- `tests/install.test.cjs` (folds former `bug-2979-hook-absolute-node`, consolidation epic #1969)
 - `tests/sh-hook-paths.test.cjs`
 - `tests/bug-3011-sdk-path-diagnostic.test.cjs`
-- `tests/bug-3017-codex-hook-absolute-node.test.cjs`
-- `tests/bug-2376-opencode-windows-home-path.test.cjs`
+- `tests/codex-config.test.cjs` (folds former `bug-3017-codex-hook-absolute-node`, consolidation epic #1969)
+- `tests/path-replacement.test.cjs` (folds former `bug-2376-opencode-windows-home-path`, consolidation epic #1969)
 - `tests/bug-3020-install-shell-path-probe.test.cjs`
 - `tests/bug-3359-stale-gsd-sdk-path-version.test.cjs`