docs(recovery): the undo runbook — generations, journals, snapper, nixos-enter (item 6d)

Slice (d) of the docs review: docs/RECOVERY.md tells the recovery
story that existed only in pieces, ordered by symptom — bad theme/HM
change (generations, apply-known-good, git-revert the flake), desktop
won't start (TTY, greetd + user journals, VM-GL and preactivate-log
pointers), broken system change (older systemd-boot generation, then
make it stick), lost files (btrfs-assistant / nomarchy-snapshots), and
the ISO + nixos-enter last resort. Commands checked against the tree;
linked from the README file tree and §5.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -30,14 +30,14 @@ surface vs tables, catches stale rows too); slice (b) drift pass over
 docs/OVERRIDES.md, docs/TESTING.md, templates/downstream/README.md —
 every factual claim spot-checked against the tree, all held; fixed the
 two gaps (OVERRIDES now routes to `nomarchy.monitors`; TESTING §1 lists
-the shell-syntax check its CI § claimed). Remaining slices:
+the shell-syntax check its CI § claimed); slice (d) recovery runbook —
+docs/RECOVERY.md (theme/HM generations → greetd journals → boot an older
+generation → snapper restore/rollback → nixos-enter), linked from the
+README tree + §5. Remaining:
 - **(c) install/first-run story** read end to end (README install §§ +
-  template README as one narrative; fix the seams).
-- **(d) recovery runbook** — short doc: desktop won't start → boot an
-  older generation / `nomarchy-snapshots` / greetd journal. The pieces
-  exist, the story isn't written.
-Site-vs-markdown is a Decision (below). **Verify:** V0 per slice; (b)/(c)
-against the live tree, not memory.
+  template README as one narrative; fix the seams) — the last slice.
+Site-vs-markdown is a Decision (below). **Verify:** V0; (c) against the
+live tree, not memory.
 
 ## NEXT
 

agent/JOURNAL.md

@@ -17,6 +17,21 @@ Template:
 
 ---
 
+## 2026-07-04 — docs slice (d): recovery runbook (iteration #15, item 6d)
+- **Task:** BACKLOG NOW#6 slice (d) — write the undo story.
+- **Did:** docs/RECOVERY.md, symptom-ordered: (1) bad theme/HM change →
+  generations / apply-known-good / git-revert ~/.nomarchy; (2) desktop
+  won't start → Ctrl+Alt+F2, greetd + user journals, VM-GL and
+  preactivate-log pointers; (3) system change → systemd-boot older
+  generation (kept: 10) + make-it-stick via sys-rebuild; (4) files →
+  btrfs-assistant / sudo nomarchy-snapshots (undochange, root rollback,
+  typed-yes); (5) ISO + nixos-enter. Every command checked against the
+  tree (greetd cfg, configurationLimit, snapshots script actions,
+  helper names). Linked from README tree + §5.
+- **Verified:** V0 (docs-only) — flake check clean pre-commit.
+- **Pending:** slice (c) install-story read-through — the last of item 6.
+- **Next suggestion:** finish item 6 with slice (c).
+
 ## 2026-07-04 — docs slice (b): drift pass (iteration #14, item 6b)
 - **Task:** BACKLOG NOW#6 slice (b) — OVERRIDES.md / TESTING.md /
   templates/downstream/README.md vs the live tree.