Repo is the install location; all scripts self-locate

Users now clone to a persistent ZFS pool and the repo stays in place.
No files are copied on install — the PREINIT hook points directly into
the clone. Scripts derive PATCH_DIR from their own path at runtime.

- install.sh: PATCH_DIR=$(dirname $0); register patch/apply.sh as
  PREINIT target; chmod only, no cp; update pipe-install error message
- patch/apply.sh: PATCH_DIR=$(dirname $0)/..; substitute PATCH_DIR
  into sitecustomize.py via sed when writing to site-packages;
  reference patch_ui.py as patch/patch_ui.py
- recover.sh, uninstall.sh: PATCH_DIR=$(dirname $0)
- uninstall.sh: look for patch/apply.sh in PREINIT registry
- patch/create_task.py: _PATCH_DIR derived from __file__; apply.log
  path in error message derived from _PATCH_DIR
- patch/sitecustomize.py: /data/truecloud-patch remains as placeholder
  substituted by apply.sh on each install
- .gitignore: exclude runtime files (apply.log, hook_status.json, disabled)
- README: document clone-to-pool install; update all example paths

.gitignore

@@ -0,0 +1,6 @@
+# Runtime files written to the repo root by apply.sh and sitecustomize.py
+/apply.log
+/apply.log.1
+/apply.log.2
+/hook_status.json
+/disabled