feat: migrate to openrouter.ai/labs/spawn CDN + release artifact version checks (#2178)

* feat: migrate shell script URLs to openrouter.ai/labs/spawn CDN

Users on older CLI versions can't auto-update because the repo was restructured
(cli/ → packages/cli/), so old version-check URLs 404. This decouples the CLI
from the repo's internal directory structure:

- Shell script URLs (install, agent scripts, github-auth) now use
  openrouter.ai/labs/spawn/* as primary with GitHub raw as fallback
- Version checks now use GitHub release artifact (cli-latest/version)
  as primary — a static URL that never changes regardless of repo layout
- CI workflow updated to publish a `version` file alongside cli.js
- Remove GITHUB_RAW_URL_PATTERN validation (no longer needed since
  install URL is now a hardcoded CDN string, not interpolated)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* style: fix biome formatting in update-check test

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: CLAUDE.md says biome lint but should say biome check

biome lint only checks lint rules, not formatting. biome check does both.
The hooks and CI already run biome check — the docs were out of sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(hooks): PostToolUse hook wasn't running biome on CLI source files

Two bugs in validate-file.ts:

1. Config search only checked 1-2 levels up from the edited file, but
   biome.json is at packages/cli/ — 3 levels above src/__tests__/*.ts.
   Fix: walk up directories until biome.json is found (or hit root).

2. Ran `biome format` (prints formatted output, always exits 0) instead
   of `biome format --check` (exits non-zero if file needs formatting).
   Fix: use `biome check` which does lint + format check in one pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/cli/src/commands/help.ts

@@ -1,5 +1,5 @@
 import pc from "picocolors";
-import { RAW_BASE, REPO } from "../manifest.js";
+import { SPAWN_CDN, REPO } from "../manifest.js";
 
 function getHelpUsageSection(): string {
   return `${pc.bold("USAGE")}
@@ -69,7 +69,7 @@ function getHelpAuthSection(): string {
 
 function getHelpInstallSection(): string {
   return `${pc.bold("INSTALL")}
-  curl -fsSL ${RAW_BASE}/sh/cli/install.sh | bash`;
+  curl -fsSL ${SPAWN_CDN}/cli/install.sh | bash`;
 }
 
 function getHelpTroubleshootingSection(): string {