refactor(packages): one manifest parser, so a name means one thing to both tools

install.sh and pkg-inventory.sh carried byte-identical copies of read_manifest.
That is the duplicated-code half of the problem; the worse half is untested —
neither script had any test for the grammar that decides what gets installed.

- scripts/lib/manifest.sh is the parser; both scripts source it
- tests/manifest-parser.bats writes the contract first (comments, CRLF, first
  field only, unreadable file fails loudly instead of yielding "nothing desired")
- an unreadable manifest now fails inside the helper rather than depending on
  whichever `set` options the caller happens to run under
- install.sh check mode verified end to end against a stubbed pacman: a CRLF
  manifest with trailing comments resolves to bare names, installed names drop

Refs #60

omp-docs/tools/packages.md

@@ -25,9 +25,13 @@ if both directions are checked.
 ## Manifests
 
 `packages/common.pkgs` (every host) + `packages/<host>.pkgs` (this host) + `packages/aur.pkgs`
-(AUR-only, installed through `yay`). The parser is `sed 's/#.*//'` then the first field, so `#`
-comments trail freely and one token per line is the whole grammar. An unknown `--host` gets the
-common manifest only: a wrong-host run is a no-op, not a hazard.
+(AUR-only, installed through `yay`). **One parser reads them for both tools**:
+`scripts/lib/manifest.sh` — `sed 's/#.*//'` then the first field, so `#` comments trail freely and
+one token per line is the whole grammar; an unreadable manifest is a loud failure rather than an
+empty desired list. `tests/manifest-parser.bats` owns that contract. The two scripts carried
+verbatim copies of the body until 2026-10-21, which is exactly how a manifest line can come to mean
+two things to the two halves of the same check. An unknown `--host` gets the common manifest only:
+a wrong-host run is a no-op, not a hazard.
 
 ## Rebuild a workstation
 
@@ -110,5 +114,6 @@ never teach a fresh box to install.
 
 - [tools/index](index.md) · [dotfiles-deploy](dotfiles-deploy.md) (the config tier that follows) ·
   [live-sync](live-sync.md) (the heartbeat that commits machine state)
-- Tests: `tests/pkg-inventory.bats` (fixtures + stubbed `pacman`, no real package database touched).
+- Tests: `tests/pkg-inventory.bats` (fixtures + stubbed `pacman`, no real package database touched)
+  and `tests/manifest-parser.bats` (the grammar above, observed as names in / names out).
 - Refs #51.

scripts/install.sh

@@ -17,7 +17,8 @@
 # otherwise sudo prompts normally. The value is never stored in this repo.
 set -euo pipefail
 
-REPO="$(git -C "$(dirname "$(realpath "$0")")" rev-parse --show-toplevel 2>/dev/null || true)"
+HERE="$(dirname "$(realpath "$0")")"
+REPO="$(git -C "$HERE" rev-parse --show-toplevel 2>/dev/null || true)"
 REPO="${INSTALL_REPO:-$REPO}"
 [ -n "$REPO" ] && [ -d "$REPO/packages" ] || { echo "install.sh: no packages/ under ${REPO:-<repo>}" >&2; exit 1; }
 
@@ -36,9 +37,7 @@ SUDO() {
   else sudo "$@"; fi
 }
 
-read_manifest() { # $1 = manifest path; emits package names, strips comments/blanks
-  sed 's/#.*//' "$1" | tr -d '\r' | awk '{if ($1) print $1}'
-}
+source "$HERE/lib/manifest.sh"   # the same parser pkg-inventory.sh reads with
 # ---- desired-minus-installed delta ------------------------------------------
 PKGS=()
 for m in common.pkgs "$HOST.pkgs"; do

scripts/lib/manifest.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# scripts/lib/manifest.sh — the one parser for packages/*.pkgs
+#
+# install.sh walks desired → installed; pkg-inventory.sh walks installed → declared. Both read the
+# same hand-written manifests, so both must agree on what a line MEANS: if one forgives an inline
+# comment and the other does not, the same name is simultaneously "desired" and "drift", and the
+# pair stops being a check on the machine. Source it — do not paste the body into a caller again
+# (Refs #60: it was pasted twice, in install.sh and in pkg-inventory.sh).
+#
+# Contract, and tests/manifest-parser.bats is that contract:
+#   name         first field of a line, emitted as one bare token — callers hand it to pacman
+#   comment      `#` and everything after it is dropped, whole-line or trailing
+#   CRLF         stripped (the manifests are edited on more than one box)
+#   blank        empty and whitespace-only rows vanish
+#   unreadable   non-zero exit, no names: a silent empty list reads as "nothing desired", and a
+#                rebuild would then install nothing while reporting success
+#
+# Sourced, never executed; callers own `set -euo pipefail`.
+
+read_manifest() { # $1 = manifest path; prints one package name per line
+  [[ -r "$1" ]] || { printf 'read_manifest: cannot read %s\n' "$1" >&2; return 2; }
+  sed 's/#.*//' "$1" | tr -d '\r' | awk '{if ($1) print $1}'
+}

tests/manifest-parser.bats

@@ -0,0 +1,51 @@
+#!/usr/bin/env bats
+# tests/manifest-parser.bats — the one manifest parser, shared by install.sh and pkg-inventory.sh
+#
+# `packages/*.pkgs` is hand-written, so the parser's whole job is to forgive the ways a hand-edited
+# list is wrong. The same function decides what install.sh tries to install and what pkg-inventory
+# calls drift, so a manifest line must mean the same thing to both — which is why it lives in one
+# file instead of being pasted into each caller (Refs #60: it was pasted twice).
+#
+# Observed through the function's exit status and stdout only:
+#   names        first field of a line, one bare token; `#` and everything after it is a comment
+#   CRLF         tolerated (the manifests get edited on more than one box)
+#   blank lines  vanish
+#   unreadable   non-zero with no names — an empty desired list must never be a silent success,
+#                because "nothing desired" is exactly what a rebuild would install
+
+setup() {
+  TEST_TMP="$(mktemp -d)"
+  LIB="$BATS_TEST_DIRNAME/../scripts/lib/manifest.sh"
+}
+
+teardown() { rm -rf "$TEST_TMP"; }
+
+parse() { # $1 = manifest contents, verbatim
+  printf '%s' "$1" > "$TEST_TMP/m.pkgs"
+  run bash -c 'source "$1"; read_manifest "$2"' _ "$LIB" "$TEST_TMP/m.pkgs"
+}
+
+@test "inline notes, full-line comments, blank rows and CRLF come out as bare names" {
+  parse $'# desired state\r\nghostty          # terminal\r\n\r\n   \r\nzoxide\r\n'
+  [ "$status" -eq 0 ]
+  [ "$(printf '%s\n' "$output" | tr '\n' ' ')" = "ghostty zoxide " ]
+}
+
+@test "only the first field of a line is a package" {
+  # install.sh hands every emitted token straight to pacman, so a stray second token on a line
+  # must never become an install target; whatever it is, the manifest did not declare it.
+  parse $'neovim extra tokens here\n'
+  [ "$output" = "neovim" ]
+}
+
+@test "a comment that names a package is not a package" {
+  parse $'# vlc\n#typora\nbun\n'
+  [ "$output" = "bun" ]
+}
+
+@test "an unreadable manifest fails loudly instead of yielding an empty desired list" {
+  run --separate-stderr bash -c 'source "$1"; read_manifest "$2"' _ "$LIB" "$TEST_TMP/nope.pkgs"
+  [ "$status" -ne 0 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *nope.pkgs* ]]
+}