stacks/ is canonical; stacks-mirror/ is drift snapshot — stop confusing the two

Decision recorded in CLAUDE.md ("Stack tree convention") and memory
(convention_stacks_vs_mirror.md):

  stacks/<stack>/                    canonical / intent. git-tracked.
                                     deploy-stack.sh reads from here.
  stacks-mirror/<host>/<stack>/      snapshot / reality. gitignored.
                                     sync-stacks.sh writes here. Used
                                     for drift inspection only — never
                                     a deploy source.

Bug this fixes: deploy-stack.sh was reading from the mirror, so edits
to stacks/llama-swap/config.yaml never reached ana-ml2. Today's
two new model entries (qwen3.6-35-a3b-heretic + qwen3.6-27b) lived
in the canonical for hours but the deploy reported "in sync" because
the script only diffed mirror vs server.

Changes:
* deploy-stack.sh: source switched from MIRROR_DIR/$HOST/$STACK to
  STACKS_DIR/$STACK. Header comment + error message updated.
* sync-stacks.sh: header explicitly identifies its role as drift
  detection; documents the diff command for comparing canonical vs
  mirror.
* stacks/llama-swap/{config.yaml → conf/config.yaml}: matches the
  deploy mapping (conf/ in canonical → /opt/docker/conf/ on host).
* CLAUDE.md: "Stack mirror (pull / push)" section rewritten as
  "Stack tree convention (canonical vs mirror)" with the role table
  + workflow rules + diff recipe. Layout diagram updated.

scripts/sync-stacks.sh

@@ -1,6 +1,13 @@
 #!/usr/bin/env bash
 # sync-stacks.sh — pull /opt/docker/{compose,conf}/<stack>/ from every
-# server into version-controlled `stacks-mirror/<host>/<stack>/`.
+# server into the gitignored `stacks-mirror/<host>/<stack>/` snapshot tree.
+#
+# Role: drift detection. The mirror reflects what's actually running on
+# each host RIGHT NOW. The canonical source of truth lives at
+# `stacks/<stack>/` (git-tracked), and `deploy-stack.sh` pushes from
+# there. Use the mirror to compare what we have to what's deployed:
+#   diff -ru stacks/<stack>/ stacks-mirror/<host>/<stack>/
+# See CLAUDE.md "Stack tree convention" for the full split.
 #
 # Layout (flat per stack):
 #   stacks-mirror/<host>/<stack>/          <- mirrors /opt/docker/compose/<stack>/