test(cli_context_stats): isolate os.homedir() so claude_md_total pin is machine-independent

Codex peer review caught this: the prior 2530 pin was computed with the real
developer machine's ~/.claude/CLAUDE.md folded into the total (findClaudeMdFiles
reads it unconditionally, and isolate-home.ts only redirects HOME on macOS).
That value would differ on any other machine and doesn't exist at all on a
fresh CI runner, so the pin was silently machine-specific and would have
failed on the very next CI run. Mock os.homedir() to the test's own isolated
tempDir, matching the pattern already used by the other tests in this file,
so claude_md_total is a pure function of the 400-byte fixture (100 tokens).

Author: Token Goat Test

tests/cli_context_stats.test.ts

@@ -177,6 +177,14 @@ describe('cli_context_stats', () => {
       fs.mkdirSync(project)
       fs.writeFileSync(path.join(project, 'CLAUDE.md'), 'x'.repeat(400))
 
+      // Pin homedir to the isolated tempDir (no .claude/CLAUDE.md there) so
+      // claude_md_total is a pure function of this fixture. Without this, findClaudeMdFiles
+      // also folds in the *real* developer's ~/.claude/CLAUDE.md (see src/cli_context_stats.ts),
+      // which is machine-specific and absent entirely on a fresh CI runner -- an exact pin against
+      // the unmocked value would be right on one machine and wrong everywhere else, including CI.
+      const homedirMock = os.homedir as unknown as ReturnType<typeof vi.fn>
+      homedirMock.mockReturnValue(tempDir)
+
       let output = ''
       const orig = process.stdout.write.bind(process.stdout)
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -188,8 +196,9 @@ describe('cli_context_stats', () => {
         ;(process.stdout as any).write = orig
       }
 
+      // 400-byte fixture file / 4 = 100 tokens (see tok() in src/cli_context_stats.ts).
       const parsed = JSON.parse(output) as { claude_md_total: number }
-      expect(parsed.claude_md_total).toBe(2530)
+      expect(parsed.claude_md_total).toBe(100)
     })
 
     it('--fix actually prunes MEMORY.md via memory_prune (not a no-op)', async () => {