fix(blender-run): unique remote job dir per local path, mirrored with --delete

draupnir review: the remote job dir was keyed on the basename alone, so two
local dirs with the same name shared one remote dir, and a rerun inherited
stale files. The dir is now <basename>-<8 hex of sha256(abs path)>, and it is
mirrored with rsync --delete, confined to that one directory. There is no rm on
a computed path. Verified: a file deleted locally is gone from the rerun's
remote dir. The /defaults stderr line is documented as harmless noise.

docs/fleettools/blender.md

@@ -24,10 +24,11 @@ scripts/blender-run -- --python-expr 'import bpy; print(bpy.app.version_string)'
 ```
 
 - Always adds `-b --factory-startup --python-exit-code 1`. Arguments go after `--`.
-- **Files:** fv-ml1 does not mount `/mnt/smithy`. `--job DIR` copies DIR to
+- **Files:** fv-ml1 does not mount `/mnt/smithy`. `--job DIR` mirrors DIR to
-  `fv-ml1:/tank/blender/jobs/<name>/`, runs with that as the working directory, and copies
+  `fv-ml1:/tank/blender/jobs/<basename>-<hash of DIR's absolute path>/`, runs with that as
-  new or changed files back into DIR. Nothing is deleted on either side. Use relative
+  the working directory, and copies new or changed files back into DIR. Nothing is ever
-  input paths inside the job.
+  deleted locally, and a rerun starts from an exact mirror, never from leftovers. Use
+  relative input paths inside the job. Do not run the same DIR twice at once.
 - **Engines headless (tested 2026-09-28):** Cycles on GPU (OptiX/CUDA), Cycles on CPU, EEVEE
   (EGL, no display needed, ~9 s with the shader compile on first use), Workbench. In 5.2 the
   EEVEE id is `BLENDER_EEVEE` (`BLENDER_EEVEE_NEXT` is gone). For Cycles GPU, set
@@ -44,7 +45,9 @@ scripts/blender-run -- --python-expr 'import bpy; print(bpy.app.version_string)'
   sets it.
 - `render.filepath` must be **absolute**. Blender does not resolve a relative output path
   against the working directory ("cannot save 'out.png'"). Importers and Python file I/O do.
-- "HIPEW initialization failed" on stderr is harmless: it is the AMD backend probing.
+- Harmless stderr noise: "HIPEW initialization failed" (the AMD backend probing), and "Failed to
+  create secure directory (/defaults): Operation not permitted" (the image's runtime-dir setup
+  running as a non-root user; reported by draupnir 2026-09-28).
 - The first OptiX render in a process includes about 1-2 s of kernel load.
 
 ## blender-mcp (agents)

scripts/blender-run

@@ -16,10 +16,12 @@
 #   output path against the working directory: "cannot save 'out.png'". Python file I/O and
 #   importers do use the cwd.
 #
-# Files: fv-ml1 does NOT mount /mnt/smithy. With --job DIR, DIR is copied to
+# Files: fv-ml1 does NOT mount /mnt/smithy. With --job DIR, DIR is mirrored to
-# fv-ml1:/tank/blender/jobs/<name>/, Blender runs WITH THAT AS ITS WORKING DIRECTORY, and new or
+# fv-ml1:/tank/blender/jobs/<basename>-<hash of DIR's absolute path>/, Blender runs WITH THAT AS ITS
-# changed files are copied back into DIR afterwards (nothing is deleted on either side). Use
+# WORKING DIRECTORY, and new or changed files are copied back into DIR afterwards (nothing is ever
-# relative paths inside the job. Without --job, the only paths Blender sees are under
+# deleted locally). Use relative paths inside the job. Running the SAME DIR twice concurrently
+# still shares one remote dir, so don't do that. Remote job dirs are never swept: one copy is kept
+# per distinct DIR (small files, on /tank). Without --job, the only paths Blender sees are under
 # /work (= fv-ml1:/tank/blender).
 #
 # Budget: GPU 3 (96 GB, borrowed from the vLLM reserve: this ends if a full-size seat moves in).
@@ -42,10 +44,16 @@ done
 WORKDIR=/work
 if [ -n "$JOB" ]; then
   [ -d "$JOB" ] || { echo "blender-run: --job $JOB is not a directory" >&2; exit 2; }
-  NAME=$(basename "$(realpath "$JOB")")
+  ABS=$(realpath "$JOB")
-  [[ $NAME =~ ^[A-Za-z0-9._-]+$ ]] || { echo "blender-run: job dir name '$NAME' must be [A-Za-z0-9._-]" >&2; exit 2; }
+  BASE=$(basename "$ABS")
+  [[ $BASE =~ ^[A-Za-z0-9._-]+$ ]] || { echo "blender-run: job dir name '$BASE' must be [A-Za-z0-9._-]" >&2; exit 2; }
+  # Keyed on basename + a hash of the ABSOLUTE local path (draupnir, 2026-09-28): two different
+  # dirs that share a basename no longer share a remote dir. `--delete` makes the remote an exact
+  # mirror of DIR, so a rerun never inherits an earlier run's leftovers. rsync removes only
+  # inside that one remote dir; there is no rm on a computed path.
+  NAME=$BASE-$(printf '%s' "$ABS" | sha256sum | cut -c1-8)
   ssh -n -o BatchMode=yes "$HOST" "mkdir -p /tank/blender/jobs/$NAME"
-  rsync -a "$JOB"/ "$HOST:/tank/blender/jobs/$NAME/"
+  rsync -a --delete "$JOB"/ "$HOST:/tank/blender/jobs/$NAME/"
   WORKDIR=/work/jobs/$NAME
 fi