fix(install): label and explain the swap-size prompt

BACKLOG #93 (Acer live pass): the swap field appeared as a bare
prefilled number — gum never renders the placeholder once --value is
set, and the block had no section header, so nothing said what the
value meant. Add a visible "Swap & hibernation" section, two info lines
(default = RAM keeps hibernation possible; 0 = no swap), a labeled
--header on the input, and make the info + Review lines state the
outcome in full ("N GiB swapfile (enables hibernation)" /
"none (hibernation disabled)"). Default behavior unchanged (swap = RAM).

Verified: V2 — interactive KVM UI drive of the built ISO; viewed
10-swap-prompt.png (section + explanations + labeled input) and the
Review box ("Swap: 6 GiB swapfile (enables hibernation)") in
/tmp/nomarchy-v2-swap-93/; the wipe confirmation was aborted, nothing
touched. bash -n + nix flake check --no-build green.

Side-finding recorded on #112: QEMU's /dev/fd0 was listed first by the
disk picker (live repro evidence in the same artifacts).

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

agent/BACKLOG.md

@@ -30,14 +30,6 @@ These are separate queue items from one real install/session pass. Preserve
 that separation when fixing them: the installer blocker, unclear installer
 copy, and post-install desktop failures have different verification paths.
 
-### 93. Installer: swap-size field lacks a clear prompt/explanation
-
-The partition value appears prefilled without a caption explaining that it is
-swap size. Keep the resolved product default (swap exactly equal to RAM), but
-label the field, state its unit/default, and explain the no-swap value. Pass =
-the summary makes the resulting swap allocation unambiguous before disk
-changes begin.
-
 ### 94. Live ISO/install: no default browser observed
 
 Chromium is the resolved default-browser decision and is present in the
@@ -155,7 +147,10 @@ effects made clear and each existing recovery path represented once.
 ### 112. Installer disk-picker safety
 
 Exclude floppy, pseudo, tiny, and otherwise non-installable devices such as
-`/dev/fd0`; never select them by default. Pass = the real install disk is clear,
+`/dev/fd0`; never select them by default. **Reproduced in QEMU 2026-07-13**
+(#93's V2 run): with OVMF the guest exposes `/dev/fd0` and the picker listed
+it FIRST — a blind Enter selected it (artifacts:
+`/tmp/nomarchy-v2-swap-93/20-review.png`, `Disk: /dev/fd0 (WILL BE ERASED)`). Pass = the real install disk is clear,
 invalid devices cannot reach destructive setup, a permanent guard covers the
 filter/default logic, and a pre-destructive KVM run proves the picker behavior.
 

agent/JOURNAL.md

@@ -19,6 +19,23 @@ Template:
 
 ---
 
+## 2026-07-13 — #93 installer swap prompt labeled + explained (this commit)
+- **Task:** BACKLOG #93 — the swap field was a bare prefilled gum input (no
+  visible section, label, or unit; the placeholder never shows once a value
+  is prefilled).
+- **Did:** `nomarchy-install.sh`: visible "Swap & hibernation" section, two
+  info lines (default = RAM ⇒ hibernation-ready; 0 = no swap), a labeled
+  `--header` on the input, and unambiguous info + Review lines
+  ("N GiB swapfile (enables hibernation)" / "none (hibernation disabled)").
+- **Verified:** V2 — full interactive KVM UI drive on the built ISO; VIEWED
+  `/tmp/nomarchy-v2-swap-93/10-swap-prompt.png` (section, both info lines,
+  labeled prefilled input) and `…/30-doctor.png` (Review box:
+  "Swap: 6 GiB swapfile (enables hibernation)"); wipe confirm aborted by
+  mismatch, nothing touched. bash -n + V0 flake check green.
+- **Pending:** side-finding: QEMU exposed `/dev/fd0` as the FIRST picker row
+  — recorded as live repro evidence on #112.
+- **Next suggestion:** #99/#107 commits from the same evidence run.
+
 ## 2026-07-13 — charge-limit start-limit-hit on spaced AC storms (this commit)
 - **Task:** Live V3 failure of #101 (TuringMachine doctor badge, 18:16): a
   spaced dock/AC event storm → 5 successful starts in 10s →

pkgs/nomarchy-install/nomarchy-install.sh

@@ -279,15 +279,20 @@ info "Encryption: $([[ $WITH_LUKS == true ]] && echo "LUKS2 (desktop auto-login)
 # ─── Swap / hibernation ─────────────────────────────────────────────────
 # A swapfile ≥ RAM on its own BTRFS subvolume makes hibernation possible;
 # the resume offset is wired into the config below.
+section "Swap & hibernation"
+
 ram_gb=$(awk '/MemTotal/ {print int(($2 + 1048575) / 1048576)}' /proc/meminfo)
 if [[ "$UNATTENDED" == "1" ]]; then
     SWAP_GB="${NOMARCHY_SWAP_GB:-$ram_gb}"
 else
+    info "A swapfile sized ≥ RAM lets this machine hibernate (suspend to disk)."
+    info "Default = ${ram_gb} GiB (this machine's RAM). Enter 0 for no swap (disables hibernation)."
     SWAP_GB=$(gum input --value "$ram_gb" \
+        --header "Swap size in GiB (default ${ram_gb} = RAM, 0 = no swap)" \
         --placeholder "swap size in GiB (≥ RAM enables hibernation, 0 = none)")
 fi
 [[ "$SWAP_GB" =~ ^[0-9]+$ ]] || fail "Swap size must be a whole number of GiB."
-info "Swap: $([[ "$SWAP_GB" == "0" ]] && echo none || echo "${SWAP_GB}G swapfile (hibernation-ready)")"
+info "Swap: $([[ "$SWAP_GB" == "0" ]] && echo "none (hibernation disabled)" || echo "${SWAP_GB} GiB swapfile (hibernation-ready)")"
 
 # ─── User account ───────────────────────────────────────────────────────
 section "Your account"
@@ -442,7 +447,7 @@ fi
 gum style --border normal --padding "0 2" \
     "Disk:       $TARGET_DISK  (WILL BE ERASED)" \
     "Encryption: $([[ $WITH_LUKS == true ]] && echo "LUKS2 + desktop auto-login" || echo none)" \
-    "Swap:       $([[ "$SWAP_GB" == "0" ]] && echo none || echo "${SWAP_GB}G (hibernation)")" \
+    "Swap:       $([[ "$SWAP_GB" == "0" ]] && echo "none (hibernation disabled)" || echo "${SWAP_GB} GiB swapfile (enables hibernation)")" \
     "User:       $USERNAME" \
     "Hostname:   $HOSTNAME_" \
     "Timezone:   $TIMEZONE" \