refactor(#1727): derive NON_CLAUDE_RUNTIMES from the capability registry (ADR-1239 Phase B) (#1728)

* refactor(#1727): derive NON_CLAUDE_RUNTIMES from the capability registry

ADR-1239 Phase B (parent #1679). NON_CLAUDE_RUNTIMES was a hand-maintained
15-element literal whose own doc-comment said "keep in sync with bin/install.js
and getDirName()" — a parallel source of truth that can drift from the
capability registry. Derive it instead:

  Object.keys(capabilityRegistry.runtimes).filter(id => id !== 'claude').sort()

The exported value is byte-identical to the old literal (the registry's
runtimes key set minus claude is exactly the 15 entries), so there is no
observable behavior change; the list can no longer drift from the registry.
capability-registry.cjs is a committed, dependency-free data module (no cycle).

Drift-guard test: golden-oracle deepEqual (non-circular) + a role-based
cross-check from the registry metadata + every member must have a non-'.claude'
getDirName branch (a registry runtime missing a getDirName branch now fails CI).

Closes #1727

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

* chore(#1727): backfill changeset PR number (#1728)

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

* fix(#1727): put docs-exempt marker on its own line so parse.cjs extracts it

DOCS_EXEMPT_RE is line-anchored (^...$ + m flag); the marker only counts on
its own line. It was appended to the end of the body text, so it was never
extracted and docs-lint failed in CI (fail_docs_missing). Verified via direct
parse.cjs extraction (docsExempt now non-empty, marker stripped from body).

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

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/non-claude-runtimes-registry-derivation.test.cjs

@@ -0,0 +1,81 @@
+'use strict';
+/**
+ * Drift-guard: NON_CLAUDE_RUNTIMES must always be derived from the capability
+ * registry. Verifies:
+ *   1. The exported constant equals a hardcoded golden expected list — a pinned
+ *      oracle that catches BOTH formula bugs (derived value diverges from golden)
+ *      AND unintended registry drift (adding/removing a runtime forces a
+ *      deliberate golden-list update).
+ *   2. Every registry entry with role === 'runtime' and id !== 'claude' appears
+ *      in NON_CLAUDE_RUNTIMES — a cross-check from a different angle than the
+ *      production derivation formula.
+ *   3. Every member of NON_CLAUDE_RUNTIMES has an explicit getDirName branch that
+ *      does not return '.claude' — guards against adding a runtime to the registry
+ *      without teaching getDirName about it (ADR-1239 Phase B, #1679).
+ *
+ * Behavioral tests only: assert on returned values, no source-grep.
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const conversion = require('../gsd-core/bin/lib/runtime-artifact-conversion.cjs');
+const registry = require('../gsd-core/bin/lib/capability-registry.cjs');
+const runtimeNamePolicy = require('../gsd-core/bin/lib/runtime-name-policy.cjs');
+
+const { NON_CLAUDE_RUNTIMES } = conversion;
+const { getDirName } = runtimeNamePolicy;
+
+// Golden oracle: hardcoded sorted known-good list of all non-Claude runtimes.
+// A pinned expected value in a TEST is correct — the test IS the oracle.
+// Only PRODUCTION code should derive dynamically from the registry.
+// If this list diverges from NON_CLAUDE_RUNTIMES, either the formula is wrong
+// OR the registry changed — both require a deliberate golden-list update here.
+const EXPECTED = [
+  'antigravity', 'augment', 'cline', 'codebuddy', 'codex', 'copilot',
+  'cursor', 'gemini', 'hermes', 'kilo', 'kimi', 'opencode', 'qwen',
+  'trae', 'windsurf',
+];
+
+test('NON_CLAUDE_RUNTIMES matches the golden expected set (sorted)', () => {
+  assert.deepEqual(
+    [...NON_CLAUDE_RUNTIMES],
+    EXPECTED,
+    `NON_CLAUDE_RUNTIMES diverged from golden list.\n` +
+    `  actual:   [${[...NON_CLAUDE_RUNTIMES].join(', ')}]\n` +
+    `  expected: [${EXPECTED.join(', ')}]`,
+  );
+  // Explicit readability assertion: 'claude' must never appear.
+  assert.ok(
+    !NON_CLAUDE_RUNTIMES.includes('claude'),
+    'NON_CLAUDE_RUNTIMES must not contain "claude"',
+  );
+});
+
+test('every registry-declared runtime except claude is present in NON_CLAUDE_RUNTIMES', () => {
+  // Cross-check from a DIFFERENT angle than the production derivation formula:
+  // iterate registry entries by their role field rather than by Object.keys().filter().
+  // This catches a case where a runtime is added to the registry with role==='runtime'
+  // but is somehow excluded from NON_CLAUDE_RUNTIMES by a formula bug.
+  for (const [id, entry] of Object.entries(registry.runtimes)) {
+    if (entry.role === 'runtime' && id !== 'claude') {
+      assert.ok(
+        NON_CLAUDE_RUNTIMES.includes(id),
+        `Registry declares runtime '${id}' (role==='runtime') but it is missing from NON_CLAUDE_RUNTIMES`,
+      );
+    }
+  }
+});
+
+// Forward direction (registry → getDirName coverage) is the load-bearing guard:
+// the registry is the authoritative runtime source, so every member of
+// NON_CLAUDE_RUNTIMES must have an explicit getDirName branch.
+test('DRIFT GUARD: every registry-declared non-Claude runtime has an explicit getDirName branch (not .claude)', () => {
+  for (const rt of NON_CLAUDE_RUNTIMES) {
+    const dir = getDirName(rt);
+    assert.notEqual(
+      dir,
+      '.claude',
+      `getDirName('${rt}') returned '.claude' — runtime '${rt}' is in the registry but missing an explicit getDirName branch`,
+    );
+  }
+});