skill: orphan the long runs (session death killed both tiers) + copy tier is not idempotent

SKILL.md

@@ -276,6 +276,8 @@ re-encoded to `-b:a 256k`: that added ~128 kbps for no audible gain, ~+10% file
 - **Never build a verification harness on a stream copy or a seek**: compare whole files, decode both sides sequentially, and prove the harness on a file against itself (must be lo=1.0).
 - **Judge a defect's SHAPE, not one frame**: mean < 0.98 or > 1% of frames below 0.85 fails; a handful of scattered low frames at a healthy mean is a fade, and SSIM on near-flat frames means nothing.
 - **Kill by PID only**, one lock per tier, one NVENC job at a time, and pause GPU tiers before a driver update (an update wedges GPU work silently — the output-growth watchdog is the net).
+- **A multi-day run must not be tied to the agent session.** Two tiers launched as Hermes background jobs with `persist_on_release` were both killed mid-encode the moment the user closed their session (measured 2026-10-08 10:37: `*_out.mp4` and `.err` frozen in the stage dir, no `PASS-DONE` in either log, ~40 min of work lost). Launch them **orphaned** instead — `powershell -NoProfile -Command "Start-Process -FilePath <bash.exe> -ArgumentList <script.sh> -WindowStyle Hidden"`, the script itself looping `library_run.py` with a retry — so the parent exits immediately and the agent's process cleanup cannot reach the tree. Verify the chain: the job's parent must be a bash whose own parent is already gone. Cost: no exit notification (watch the log) and **stopping is by PID only**.
+- **The `copy` tier is not idempotent — never re-run a whole `--tier copy` pass.** Its only skip test is "already HEVC hvc1", and a copy output is H.264 by definition, so a second pass redoes every file it ever produced (193 of them here, ~40 GB of share I/O). For a handful of newly-arrived files use the single-file path per file: `library_run.py --tier copy --path <file> --keep-source`.
 - **Full measured detail, every failure mode and its detector: `references/pitfalls.md`.**
 
 ## The owner's standing requirements — read this first