fix(test): update four main-side assertions to the T3 installer contracts

Integration drift from the T3 lane: three static assertions pinned the OLD
implementation shapes that T3 legitimately replaced — the gbrain-refresh
branch no longer self-documents a reset --hard cycle (#2569 renders to an
untracked out-dir instead; the test now pins THAT), setup's regen block
renamed to the render form (re-anchored, same exit-code-propagation
invariant), and sections/ linking generalized into _link_skill_runtime_assets
(the _link_or_copy routing assertion moved into the helper). Fourth: the
uninstall neutral-target test asserted against os.tmpdir(), which reads
$TMPDIR at call time — a shard neighbor can leave it gstack-containing,
making the "neutral" symlink target match the provenance substring; the test
now falls back to a fixed neutral root and asserts neutrality explicitly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/gbrain-refresh-install-render.test.ts

@@ -44,13 +44,18 @@ describe('gstack-config gbrain-refresh: machine-wide render guards', () => {
     expect(branch).toContain('command -v bun');
   });
 
-  test('renders the :user variant in place into the install', () => {
+  test('renders the :user variant for the claude host', () => {
     expect(branch).toContain('gen:skill-docs:user --host claude');
   });
 
-  test('is self-documenting about the reset --hard / re-run cycle', () => {
-    expect(branch).toContain('reset --hard');
-    expect(branch).toContain('gbrain-refresh');
+  // #2569: the render goes to an UNTRACKED out-dir, never in place — the old
+  // in-place render dirtied the install checkout on every refresh, and this
+  // branch used to self-document a reset --hard / re-run cycle as the
+  // workaround. The out-dir render makes that cycle unnecessary.
+  test('renders to an untracked out-dir, never in place (#2569)', () => {
+    expect(branch).toContain('--out-dir');
+    expect(branch).toContain('render/claude');
+    expect(branch).not.toContain('reset --hard');
   });
 });