enh(#2876): retire the dead and pass-through exports from bin/install.js (#3615)

* enh(#2876): retire the dead and pass-through exports from bin/install.js

The installer exported 197 names and had zero production consumers - every
non-test require of it repo-wide sits inside a comment. Its interface was
shaped by test access, not by callers.

Removes 9 dead exports and 61 pass-throughs, repointing their tests onto the
extracted modules' own interfaces. 197 down to 127.

Every count in the issue was wrong: 197 exports not 188, 9 dead not 12, 61
pass-throughs not 49, 44 test files not 42 - and the audit itself then missed
7 more consumer files. restoreUserArtifacts was on the dead list but ceased to
exist in phase 6, and two _GSD_EFFORT_MANIFEST_* names listed as dead are now
genuinely asserted, so acting on that list would have deleted live exports.

7 of the 9 dead names collide with an independent declaration that install.js
delegates TO. Each removal was justified by which declaration a reference
resolves to, never by whether the name appears somewhere.

Coverage parity was the gate rather than test greenness: per-file counts were
captured before any edit and diffed after. 44 of 45 files are byte-identical;
the single delta is one added assertion, not a loss.

The sweep for scattered require sites found two forms static grep misses -
require(VARIABLE) and multi-line require() - plus tests asserting that
install.js re-exports the SAME object, which now assert retirement instead.

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

* fix(#2876): close review findings — restore the duplicate-body guard, sweep orphaned code

Both review engines found real defects in the first cut.

The DEFECT.GENERATIVE-FIX single-owner guard from #1511 had been repointed
from a reference-identity check to install.X === undefined. Those are not
equivalent: the guard exists to catch a duplicate function body reintroduced
into install.js, and the replacement passes cleanly if that duplicate is used
internally and never exported. It now walks bin/install.js's real top-level
bindings, so it catches a duplicate under either shape, exported or not -
strictly stronger than the check it replaced. Proved by injecting a duplicate
and watching it go red.

That weakening survived the coverage-parity gate because the assertion count
never moved. The gate compares counts, so an assertion that changes meaning
rather than number is invisible to it.

Removing the exports had orphaned their wrapper bodies: 14 dead wrappers, 9
consts and 9 destructure entries, several pre-existing and found by the same
sweep. Dead code left in the file this phase exists to shrink.

Three more comments claimed re-exports this phase removed, and tests were
reading Cursor and Windsurf hook constants from install.js's local copy while
calling functions from the hooks surface - equal today, with nothing holding
them equal. The local consts now reference the owning module.

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

* chore(#2876): backfill changeset pr number

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

---------

Co-authored-by: sim <sim@local>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

tests/cursor-conversion.test.cjs

@@ -14,8 +14,10 @@ const assert = require('node:assert/strict');
 const {
   convertClaudeCommandToCursorSkill,
   convertClaudeAgentToCursorAgent,
-  _applyRuntimeRewrites,
 } = require('../bin/install.js');
+const {
+  _applyRuntimeRewrites,
+} = require('../gsd-core/bin/lib/runtime-artifact-conversion.cjs');
 
 describe('convertClaudeCommandToCursorSkill', () => {
   test('writes unquoted Cursor skill name in frontmatter', () => {