fix(scripts): add os.homedir() fallback for Windows compatibility

On Windows (native cmd/PowerShell), process.env.HOME is undefined.
Seven CLI entry points and two library files pass process.env.HOME
directly as homeDir without a cross-platform fallback, causing all
path resolutions to silently fail (resolving to "undefined/.claude/...").

Node.js os.homedir() correctly handles all platforms (HOME on Unix,
USERPROFILE on Windows, OS-level fallback). The project already uses
this pattern in scripts/lib/state-store/index.js and has a getHomeDir()
utility in scripts/lib/utils.js, but it was not applied consistently.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Signed-off-by: Lidang-Jiang <lidangjiang@gmail.com>

scripts/install-apply.js

@@ -6,6 +6,7 @@
  * target-specific mutation logic into testable Node code.
  */
 
+const os = require('os');
 const {
   SUPPORTED_INSTALL_TARGETS,
   listLegacyCompatibilityLanguages,
@@ -118,7 +119,7 @@ function main() {
     });
     const plan = createInstallPlanFromRequest(request, {
       projectRoot: process.cwd(),
-      homeDir: process.env.HOME,
+      homeDir: process.env.HOME || os.homedir(),
       claudeRulesDir: process.env.CLAUDE_RULES_DIR || null,
     });