fix(installer): avoid staged and installed capture class collision

docs/netplan-v4-application.md

@@ -95,3 +95,37 @@ commissioning. Economic replay-based automatic family selection, full corrected
 feedback/control integration, long-term outbox/server retention and real live/
 failure acceptance remain open. Existing trial gates are unchanged. No sensor,
 accounting or hardware evidence identifier is fabricated by data ingestion.
+
+## Installer class-path correction (2026-10-03)
+
+The original commissioning installer loaded `source/libs/NetzfahrplanV4Messaufnahme.php`
+while importing observation history. A later Manager callback loads the installed
+copy at `modules/Enelix-EMS/libs/NetzfahrplanV4Messaufnahme.php`. PHP's once-only file
+inclusion does not deduplicate class declarations across those different files.
+The dependent `NetzfahrplanV4Bilanzierung` class is subject to the same collision.
+
+The tested installer-only fix is preserved in
+`examples/V4ApplicationData/application-class-loading.patch` (SHA256
+`6d53d74d4059bb1ae3a446350637a4f4a4a73cc2fd64d2fc2f0967bd23ec7173`).
+When building a commissioning package, load both classes only from the installed
+module tree, after validating their expected source hashes. Before any require,
+check both already-loaded origins without autoload. Reject a foreign staged origin
+with a controlled error; do not hide it by wrapping the class declaration in a guard.
+Include `installed_capture_bootstrap.php` in the package checksum map. Do not change
+the installed-module manifest or bless unrelated source changes.
+
+The Lihrenmoos staging entrypoint has this fix applied, with backups of its original
+installer and checksum map. No running modules, data files, timers, native callbacks,
+server components or actuator settings were changed by the repair. Actual completion
+still requires the user's fresh Symcon invocation of the corrected installer.
+
+Validation: the original two-path failure was reproduced with the real PHP classes.
+Thirteen additional isolated installer scenarios passed, including callback/reload
+loading order, preloaded dependencies, history import, repeat/finished import,
+foreign-class refusal, partial-import preservation, source drift, registration wait
+and first installation. These are PHP CLI tests with mocked IPS in temporary trees,
+not a completed test in the actual Symcon kernel.
+
+Evidence on the test host:
+`/srv/agent/netplan-v4-application-build/class-loading-fix/TEST_RESULTS.json` and
+`FIX_RESULT.json`. The test harness and exact candidate source are retained there.