fix: platform reads a manifest whose last line lacks a newline

`while IFS='=' read -r k v` drops an unterminated final line: read returns
1 at EOF even having filled k and v. A manifest ending `bootstrapped=...Z`
with no trailing \n rendered `RIG 1.2.3` with the timestamp silently gone
— the version read fine, so nothing looked wrong.

Guarded with `|| [ -n "$k" ]`, the same shape parse_users_file already
uses (lib/users-config.sh:47). #61's writer should not have to know
whether this reader tolerates a missing newline.

Also make human_b fall back like human_kb. With numfmt absent, memory
degraded to a raw number while disk printed 'unknown' beside it, from data
already in hand.

Both found in review of #74.

Refs #64

commands/platform.sh

@@ -97,7 +97,10 @@ if DF="$(df -PB1 / 2>/dev/null)"; then
   DISK_TOTAL="$(printf '%s\n' "$DF" | awk 'NR==2 {print $2}')"
   DISK_FREE="$(printf '%s\n' "$DF" | awk 'NR==2 {print $4}')"
 fi
-human_b() { [ -n "${1:-}" ] && numfmt --to=iec-i "$1" 2>/dev/null || printf 'unknown'; }
+human_b() {   # bytes -> IEC; falls back like human_kb rather than to 'unknown'
+  [ -n "${1:-}" ] || { printf 'unknown'; return 0; }
+  numfmt --to=iec-i "$1" 2>/dev/null || printf '%s B' "$1"
+}
 
 # --- virtualization ---------------------------------------------------------
 # THE set -e TRAP: systemd-detect-virt exits NON-ZERO on bare metal while
@@ -139,7 +142,11 @@ MARKER="${RIG_ROLE_MARKER:-/etc/rig/role}"
 manifest_field() {   # $1 = key — empty when absent, unreadable or unset
   local k v
   [ -r "$MANIFEST" ] || return 0
-  while IFS='=' read -r k v; do
+  # `|| [ -n "$k" ]` so a manifest whose last line lacks a trailing newline
+  # still yields that line: read returns 1 at EOF even having filled k/v.
+  # Same guard parse_users_file uses (lib/users-config.sh:47) — #61's writer
+  # should not have to know whether this reader tolerates a missing \n.
+  while IFS='=' read -r k v || [ -n "$k" ]; do
     [ "$k" = "$1" ] || continue
     printf '%s\n' "$v"
     return 0

test/cli.sh

@@ -1017,6 +1017,13 @@ check "platform: reads the manifest version" 0 "9.9.9" \
   env RIG_MANIFEST="$PLATWORK/manifest" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
 check "platform: reads the manifest timestamp" 0 "bootstrapped 2026-07-19T14:24:51Z" \
   env RIG_MANIFEST="$PLATWORK/manifest" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
+# ...including one whose last line has no trailing newline: `read` returns 1 at
+# EOF even having filled the variables, so an unguarded loop drops that line
+# silently — the timestamp would vanish while the version still rendered. #61's
+# writer must not have to know this reader's tolerances (found in #74 review).
+printf 'version=9.9.9\nbootstrapped=2026-07-19T14:24:51Z' > "$PLATWORK/manifest-nonl"
+check "platform: reads a manifest with no trailing newline" 0 "bootstrapped 2026-07-19T14:24:51Z" \
+  env RIG_MANIFEST="$PLATWORK/manifest-nonl" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
 printf 'role=dev class=human host=yes join=authkey\n' > "$PLATWORK/role"
 check "platform: renders the role marker's traits" 0 "dev (class=human host=yes join=authkey)" \
   env RIG_MANIFEST="$PLATWORK/absent" RIG_ROLE_MARKER="$PLATWORK/role" "$ROOT/bin/rig" platform