test(#3147): bound the lint/changeset/docs cluster onto the process seam (#3181)

* test(#3147): bound the lint/changeset/docs cluster onto the process seam

Migrates 69 unbounded sync spawn sites across 24 files. Allowlist 73 to 49.

Two shared helpers move: tests/helpers/graphify.cjs (6 importing suites) and
tests/fixtures/index.cjs, whose three quoted-argument shell strings became
single argv elements rather than whitespace splits.

changeset-lint's throw-native git() helper routes to gitOrThrow; migrating it
to bare runGit would have silently swallowed a failure that is loud today.
ingest-docs goes the other way -- its catch never rethrew, it degraded failure
into data every call site asserts on, so throwIfFailed would have thrown where
the original returned. The design doc said otherwise and was corrected.

tsconfig-noemit runs a real tsc --noEmit and takes a bespoke 180000ms per the
ensure-runtime-build precedent, not the 30000ms build-hooks norm -- that norm
is for a file copy, and sizing against a label rather than the work is the
same error in the opposite direction.

* test(#3147): add toLegacyResult and settle review findings

The seam exposed a throwing adapter (throwIfFailed) but no non-throwing one,
so eight files independently re-derived the same unwrap back to the legacy
{status, stdout, stderr} shape. That is the third time this epic produced N
copies of one mechanism -- seven throw wrappers in Wave 1, fifty-two timeout
constants in Wave 2, eight result adapters here. The pattern is that whenever
the seam does not expose a mechanism, every suite re-derives it.

toLegacyResult now sits beside throwIfFailed, with its own tests.

Two sites are deliberately NOT converted: changeset-cli's runRender and
runRenderIn return {status, report, stderr} from parsed JSON and never a raw
stdout, so they are a different shape family. lint-legacy-dir-name keeps its
local GUARD_TIMEOUT_MS: 30000 matches the build norm numerically but bounds a
lint probe, not hooks bundling, and importing it would encode a coincidence
as a relationship.

---------

Co-authored-by: sim <sim@local>

tests/graphify-auto-update.slow.test.cjs

@@ -12,9 +12,10 @@ const assert = require('node:assert/strict');
 const fs = require('fs');
 const path = require('path');
 const os = require('node:os');
-const { execFileSync, spawnSync } = require('child_process');
 const { createTempProject, cleanup, runGsdTools, delay } = require('./helpers.cjs');
-const { runHook: seamRunHook } = require('./helpers/process-seam.cjs');
+const { runGit, runHook: seamRunHook } = require('./helpers/process-seam.cjs');
+const { gitOrThrow } = require('./helpers/git-fixture.cjs');
+const { PROBE_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const {
   graphifyStatus,
@@ -206,15 +207,15 @@ describe('auto-update', () => {
 
   function createTempGitRepo(opts = {}) {
     const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-3347-'));
-    spawnSync('git', ['init', '-b', opts.defaultBranch || 'main'], {
-      cwd: tmpDir,
-      stdio: 'ignore',
-    });
-    execFileSync('git', ['config', 'user.email', 'test@example.com'], { cwd: tmpDir });
-    execFileSync('git', ['config', 'user.name', 'Test'], { cwd: tmpDir });
+    // Original discarded the result unchecked (stdio: 'ignore', never a
+    // throw-native execFileSync) — bare runGit preserves that never-throws,
+    // ignored-result shape.
+    runGit(['init', '-b', opts.defaultBranch || 'main'], { cwd: tmpDir });
+    gitOrThrow(['config', 'user.email', 'test@example.com'], { cwd: tmpDir });
+    gitOrThrow(['config', 'user.name', 'Test'], { cwd: tmpDir });
     fs.writeFileSync(path.join(tmpDir, 'README.md'), '# test\n');
-    execFileSync('git', ['add', 'README.md'], { cwd: tmpDir });
-    execFileSync('git', ['commit', '-m', 'init'], { cwd: tmpDir, stdio: 'ignore' });
+    gitOrThrow(['add', 'README.md'], { cwd: tmpDir });
+    gitOrThrow(['commit', '-m', 'init'], { cwd: tmpDir });
 
     fs.mkdirSync(path.join(tmpDir, '.planning'), { recursive: true });
     if (opts.config !== undefined) {
@@ -254,6 +255,9 @@ describe('auto-update', () => {
     // suite and the hook itself dispatches a detached graphify rebuild that
     // some tests wait on separately; the hook's own synchronous return (gate
     // checks + status-file write) is fast, so 30s stays generous headroom.
+    // Original invoked the hook with stdio: 'ignore' — the seam always
+    // captures stdout/stderr instead, but every call site of this wrapper
+    // below reads only `.status`; the captured output is simply unread.
     const r = seamRunHook(HOOK, [], {
       interpreter: 'bash',
       cwd: tmpDir,
@@ -305,7 +309,14 @@ describe('auto-update', () => {
       try {
         const pid = parseInt(fs.readFileSync(lockPath, 'utf8'), 10);
         if (!Number.isFinite(pid) || pid <= 0) break;
-        execFileSync('kill', ['-0', String(pid)], { stdio: 'ignore' });
+        // `kill -0` on a live PID exits 0; on a dead PID (or missing `kill`)
+        // it exits non-zero — this loop only cares about that distinction,
+        // so it reads exitCode as data instead of preserving a throw.
+        // Original ran with stdio: 'ignore' — the seam always captures
+        // stdout/stderr instead, but only `probe.exitCode` is read below;
+        // the captured output is simply unread.
+        const probe = seamRunHook('-0', [String(pid)], { interpreter: 'kill', timeoutMs: PROBE_TIMEOUT_MS });
+        if (probe.exitCode !== 0) break; // PID dead → safe to clean up
       } catch {
         break; // PID dead → safe to clean up
       }
@@ -386,10 +397,7 @@ describe('auto-update', () => {
         config: { graphify: { enabled: true, auto_update: true } },
       });
       t.after(() => cleanupHookRepo(tmpDir));
-      execFileSync('git', ['checkout', '-b', 'worktree-agent-abc'], {
-        cwd: tmpDir,
-        stdio: 'ignore',
-      });
+      gitOrThrow(['checkout', '-b', 'worktree-agent-abc'], { cwd: tmpDir });
       const mockBin = makeMockGraphifyBin(tmpDir);
       const r = runHook(
         tmpDir,