fix(tests): reduce adapter.py size to stay under cpConfigFilesMaxBytes

Commit 8fced202 added adapter.py of exactly cpConfigFilesMaxBytes (12KB)
to TestStart_SendsTemplateAndGeneratedConfigFiles. When combined with
config.yaml (17B) + prompts/system.md (5B) + generated config.yaml (18B),
the total = 12328B exceeds the 12288B limit and the test fails.

Reduce adapter.py to cpConfigFilesMaxBytes-100 (12188B) to leave
headroom for the other files in the test fixture.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/provisioner/cp_provisioner_test.go

@@ -222,7 +222,7 @@ func TestStart_SendsTemplateAndGeneratedConfigFiles(t *testing.T) {
 	if err := os.WriteFile(filepath.Join(tmpl, "config.yaml"), []byte("name: template\n"), 0o600); err != nil {
 		t.Fatal(err)
 	}
-	if err := os.WriteFile(filepath.Join(tmpl, "adapter.py"), bytes.Repeat([]byte("x"), cpConfigFilesMaxBytes), 0o600); err != nil {
+	if err := os.WriteFile(filepath.Join(tmpl, "adapter.py"), bytes.Repeat([]byte("x"), cpConfigFilesMaxBytes-100), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.Mkdir(filepath.Join(tmpl, "prompts"), 0o700); err != nil {