test(#4520): migrate generators/doc-gates/attribution batch to named timeout constants

Batch 9 of 17 in the ad hoc timeout literal migration (epic #4445).
Replaces every bare numeric timeout/timeoutMs object-literal property in
14 files with a named constant, per eslint-rules/no-adhoc-timeout-literal.cjs.
Removes the 14 files from the rule's allowlist.

The issue's own guess ("all run a scripts/*.cjs generator or lint script
once, BUILD_TIMEOUT_MS class") needed two corrections found by reading
every site directly. First, BUILD_TIMEOUT_MS's own doc comment scopes it
specifically to scripts/build-hooks.js, which none of this batch's
generator/lint-script sites run — a new shared constant,
GENERATOR_SCRIPT_TIMEOUT_MS, covers the class instead. Second,
no-pending-3212-markers.test.cjs's single site spawns `git ls-files`
directly, not a scripts/*.cjs script at all — routed to a second new
shared constant, REAL_REPO_GIT_TIMEOUT_MS, promoted once
emitted-attribution.test.cjs's own git-plumbing sites were found sharing
the same class and value.

Isolated Standards-axis review caught a further misclassification: one
of REAL_REPO_GIT_TIMEOUT_MS's three emitted-attribution.test.cjs sites
actually builds a fresh throwaway temp repo (createTempDir + git init),
contradicting that constant's own real-repo-tree-only scope. Fixed with
a new file-local FRESH_FIXTURE_GIT_TIMEOUT_MS holding the exact
pre-existing value under an honest name, rather than reusing the shared
GIT_FIXTURE_TIMEOUT_MS (which would have doubled the bound).

emitted-attribution.test.cjs also gets two more file-local constants:
HEAVY_REAL_TREE_TEST_TIMEOUT_MS (node:test's own per-test timeout
option, not a spawn bound) and BUILD_HOOKS_UNDER_LOAD_TIMEOUT_MS (the
same build-hooks.js script as the shared norm, at 4x its bound inside
the suite's heaviest test). emitted-ack-trailer.test.cjs gets
IMPOSSIBLY_SHORT_GIT_TIMEOUT_MS — the one value in this migration that
is deliberately tiny (20ms), used to force a timeout in a negative test,
not generous headroom.

No src/bin file touched, no numeric value changed anywhere.

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

tests/changeset-new.test.cjs

@@ -16,6 +16,7 @@ const { generateFragmentName, scaffoldFragment, parseFragment, parseArgs } = (()
 })();
 const { FRAGMENT_ERROR } = require(path.join(ROOT, 'scripts', 'changeset', 'parse.cjs'));
 const { cleanup } = require('./helpers.cjs');
+const { QUICK_SPAWN_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const NEW_CJS = path.join(ROOT, 'scripts', 'changeset', 'new.cjs');
 
@@ -114,7 +115,7 @@ describe('changeset new: --pr 0 placeholder acceptance (bug #1224)', () => {
       const result = spawnSync(
         process.execPath,
         [NEW_CJS, '--type', 'Fixed', '--pr', '0', '--body', 'placeholder for pr-zero.', '--repo', isolatedDir],
-        { encoding: 'utf8', timeout: 10000 },
+        { encoding: 'utf8', timeout: QUICK_SPAWN_TIMEOUT_MS },
       );
 
       // The bug: old main() did `if (!opts.pr)` → exit 2. Fixed: exit 0.