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/api-coverage.test.cjs

@@ -17,6 +17,7 @@ const assert = require('node:assert/strict');
 const { spawnSync } = require('node:child_process');
 const path = require('node:path');
 const fc = require('fast-check');
+const { PROBE_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const MODULE_PATH = path.join(__dirname, '..', 'gsd-core', 'bin', 'lib', 'api-coverage.cjs');
 
@@ -985,7 +986,7 @@ describe('api-coverage CLI — STDIN + exit codes', () => {
     const r = spawnSync(process.execPath, [CLI, '--json'], {
       input: stdin,
       encoding: 'utf-8',
-      timeout: 15000,
+      timeout: PROBE_TIMEOUT_MS,
     });
     return { exitCode: r.status, stdout: r.stdout, stderr: r.stderr };
   }
@@ -1016,7 +1017,6 @@ describe('api-coverage CLI — NO_INPUT / UNAVAILABLE (ADR-3889 Phase 3, #3907)'
   const INJECT_STDIN_ERROR = path.join(__dirname, 'helpers', 'inject-stdin-error.cjs');
   const { exitCodeFor } = require('../gsd-core/bin/lib/exit-code-registry.cjs');
   const { runNode } = require('./helpers/process-seam.cjs');
-  const { PROBE_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
   function runCliJson(stdin, extraArgs = [], extraEnv = {}) {
     const r = runNode([CLI, '--json', ...extraArgs], {