fix(cli): hard-exit on Node 25.x instead of soft warning + crash (#149)

The Node 25.x V8 turboshaft WASM JIT Zone allocator bug
(https://github.com/colbymchenry/codegraph/issues/81) reliably crashes
CodeGraph mid-indexing with `Fatal process out of memory: Zone` when
tree-sitter grammars get JIT-compiled. We already had:

- `engines: "node": ">=18.0.0 <25.0.0"` in package.json
- Lazy grammar loading (#61)
- A startup `console.warn` when Node 25+ is detected

But the recurring duplicates (#54, #81, #140, plus comments from
multiple unique users) show those defenses aren't enough:

- npm `engines` is a soft warning by default, so `npm install -g`
  doesn't block.
- The startup `console.warn` is a single yellow line that scrolls
  off-screen before the OOM 30 seconds later, so users connect the
  crash to "CodeGraph is broken" rather than "I'm on the wrong Node
  version" and file a fresh issue.

This patch turns the soft warning into a hard exit. On Node 25+ we
print a bordered banner that names the V8 root cause, embeds the
detected version, gives Node 22 LTS install commands (nvm + Homebrew),
and links to #81 — then exit(1) BEFORE any tree-sitter import
triggers WASM JIT. The previous behaviour is preserved behind
`CODEGRAPH_ALLOW_UNSAFE_NODE=1` for anyone who patched V8 themselves
or wants to test a future Node 25 fix.

The banner builder is extracted to `src/bin/node-version-check.ts` so
the test can import it without triggering CLI bootstrap. Five unit
tests pin the version interpolation, root-cause explanation, recovery
commands (nvm + brew), override env var, and #81 link — these are
load-bearing and shouldn't get edited away silently.

Suite: 509 → 514, all passing. Verified both paths manually by
flipping the threshold to 22 in dist and running on Node 22.20.0:
without the env var the CLI prints the banner and exits 1; with
`CODEGRAPH_ALLOW_UNSAFE_NODE=1` it prints the banner and continues.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/bin/codegraph.ts

@@ -24,6 +24,8 @@ import * as fs from 'fs';
 import { getCodeGraphDir, isInitialized } from '../directory';
 import { createShimmerProgress } from '../ui/shimmer-progress';
 
+import { buildNode25BlockBanner } from './node-version-check';
+
 // Lazy-load heavy modules (CodeGraph, runInstaller) to keep CLI startup fast.
 async function loadCodeGraph(): Promise<typeof import('../index')> {
   try {
@@ -44,20 +46,21 @@ async function loadCodeGraph(): Promise<typeof import('../index')> {
 const importESM = new Function('specifier', 'return import(specifier)') as
   (specifier: string) => Promise<typeof import('@clack/prompts')>;
 
-// Warn about unsupported Node.js versions (Node 25+ has V8 turboshaft WASM bugs)
+// Block CodeGraph on Node.js 25.x — V8's turboshaft WASM JIT has a Zone
+// allocator bug that reliably crashes when compiling tree-sitter
+// grammars (see #54, #81, #140). The previous behaviour was a soft
+// console.warn that scrolls off-screen before the OOM crash 30 seconds
+// later, leading to a steady stream of "what is this OOM" reports.
+// Hard-exit before any WASM work; allow override via env var for users
+// who patched V8 themselves or want to test a future fix.
 const nodeVersion = process.versions.node;
 const nodeMajor = parseInt(nodeVersion.split('.')[0] ?? '0', 10);
 if (nodeMajor >= 25) {
-  console.warn(
-    '\x1b[33m⚠\x1b[0m  CodeGraph may crash on Node.js %s due to a V8 WASM compiler bug in Node 25+.',
-    nodeVersion
-  );
-  console.warn(
-    '   Please use Node.js 22 LTS instead: https://nodejs.org/en/download'
-  );
-  console.warn(
-    '   See: https://github.com/colbymchenry/codegraph/issues/81\n'
-  );
+  process.stderr.write(buildNode25BlockBanner(nodeVersion) + '\n');
+  if (!process.env.CODEGRAPH_ALLOW_UNSAFE_NODE) {
+    process.exit(1);
+  }
+  // Override active — banner shown for visibility, continuing.
 }
 
 // Check if running with no arguments - run installer

src/bin/node-version-check.ts

@@ -0,0 +1,36 @@
+/**
+ * Node.js version compatibility check.
+ *
+ * Node 25.x has a V8 turboshaft WASM JIT Zone allocator bug that
+ * reliably crashes CodeGraph with `Fatal process out of memory: Zone`
+ * during tree-sitter grammar compilation. This module owns the
+ * user-facing banner shown before exit. Kept side-effect-free so it's
+ * safe to import from tests without triggering CLI bootstrap.
+ */
+
+/**
+ * Build the bordered banner shown when CodeGraph detects an
+ * unsupported Node.js major version (currently 25+). Pinned via unit
+ * test so the recovery commands and override instructions can't be
+ * silently stripped by future edits.
+ */
+export function buildNode25BlockBanner(nodeVersion: string): string {
+  const sep = '─'.repeat(72);
+  return [
+    sep,
+    `[CodeGraph] Unsupported Node.js version: ${nodeVersion}`,
+    sep,
+    'Node.js 25.x has a V8 WASM JIT (turboshaft) Zone allocator bug that',
+    'crashes with `Fatal process out of memory: Zone` when CodeGraph',
+    'compiles tree-sitter grammars. CodeGraph WILL crash on this Node',
+    'version mid-indexing. See https://github.com/colbymchenry/codegraph/issues/81',
+    '',
+    'Fix: install Node.js 22 LTS:',
+    '  nvm install 22 && nvm use 22                          # nvm',
+    '  brew install node@22 && brew link --overwrite --force node@22  # Homebrew',
+    '',
+    'To override (NOT recommended — you will likely OOM):',
+    '  CODEGRAPH_ALLOW_UNSAFE_NODE=1 codegraph ...',
+    sep,
+  ].join('\n');
+}