Consolidate the sticky-Manual rule for oneliner.json into a single
helper paths::delete_oneliner_unless_manual that holds the per-case
lock, reads the state, keeps OnelinerState::Manual, and removes any
LLM-derived variant. Three previously-direct deletion paths now route
through it: handle_delete_recording, reset_case_artefacts (admin
single-reset), and bulk_reset (admin bulk action). Before this fix a
clinician's manual override was wiped by a recording delete, letting
the LLM auto-regen path overwrite it on the next view.
Tests: 4 unit tests for the wrapper contract, integration tests for
the recording-delete and case-reset endpoints (Manual preserved,
Ready wiped), and a static-scan invariant that fails on direct
remove_file(... ONELINER_FILENAME) calls outside paths.rs.
