feat(cli): a Makefile, a man page, and --help

Three things the project had no answer for: how to install it without
knowing dune, where to read about it, and what it does when asked.

Makefile, same shape as lectio's -- PREFIX ?= $(HOME)/.local, BINDIR,
MANDIR, and the '## '-comment help target -- so the two siblings are
driven the same way. Every recipe wraps dune in `opam exec --`, which is
the actual point of having one here: `make build` works from a plain
shell with no `eval $(opam env)` first. install goes through `dune
install` rather than a hand-rolled copy, because the binary finds its
calendar data relative to its own path; the man page is installed
separately to share/man/man1, matching lectio. install and uninstall
were both run against a scratch prefix and checked: uninstall leaves
zero files behind.

PREFIX defaults to ~/.local because that is where lectio installs and
where it actually lives on this machine, so colitur lands on an existing
PATH with no shell change. An earlier install this session went to
~/opt/colitur, which was me over-applying a rule meant for third-party
tools to one of the author's own projects; it has been removed rather
than left as a second, staler binary competing on PATH.

man/colitur.1 documents the four commands, both output formats and why
they differ, COLITUR_DATA_DIR and its refusal to fall back, the data
resolution order, exit statuses, and -- deliberately -- the limitations:
EF only, Epistle and Gospel only with the chants unbuilt and rejected
rather than guessed, and the BVM Saturday Mass-selection gap. A man page
that only lists what works is half a man page. Renders clean under
`groff -ww -z`, no warnings.

--help prints to stdout and exits 0; a usage error prints one line to
stderr and exits 2. That is the Unix convention rather than a
preference: asking for help succeeded and should be pipeable, being
invoked wrongly did not and must not pollute stdout. Both directions are
asserted in cli.t, along with a loop confirming every command the help
text advertises is one the dispatch actually accepts -- the check that
catches help drifting away from the code.

1 files changed, 219 insertions, 0 deletions

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+.TH COLITUR 1 "2026" "colitur" "User Commands"
+.SH NAME
+colitur \- deterministic liturgical calendar and lectionary engine (Roman rite, 1962)
+.SH SYNOPSIS
+.B colitur
+.BR easter | temporal | day | readings
+.I YEAR
+.br
+.B colitur
+.BR \-h | \-\-help
+.SH DESCRIPTION
+.B colitur
+computes the liturgical calendar of the 1962 Roman Missal \(em the
+Extraordinary Form \(em and the Mass reading citations for every day, entirely
+offline and without a network. Its name is
+.I computus liturgicus
+crossed with the Latin
+.IR colitur ,
+"He is worshipped".
+.PP
+For each day it resolves the season, the week, the observed celebration with
+its rank and colour, any commemorations, any transfers, and the day's Epistle
+and Gospel. It emits reading
+.I references
+only \(em
+.RB \(lq "Jn 3:16" \(rq
+\(em and never scripture text.
+.PP
+The engine is total and deterministic over the whole domain
+.BR "1583..9999" .
+It reads no clock, draws no randomness, and given the same data produces the
+same answer for any year in range. Years outside the domain are refused at the
+boundary rather than approximated.
+.PP
+Each report covers 1 January to 31 December of the civil
+.IR YEAR .
+That is deliberately not a liturgical year, which is Advent\-anchored and
+straddles two civil years;
+.B colitur
+resolves both liturgical years that touch the requested civil one and prints
+the civil slice.
+.SH COMMANDS
+.TP
+.BI easter " YEAR"
+Easter and the movable feasts anchored to it \(em Ash Wednesday, Palm Sunday,
+Ascension, Pentecost, Corpus Christi \(em one per line, as
+.RI \(lq name " " date \(rq.
+.TP
+.BI temporal " YEAR"
+The temporal cycle alone, one line per day, before the sanctoral calendar is
+resolved against it. Chiefly useful for inspecting season and week boundaries
+in isolation.
+.TP
+.BI day " YEAR"
+The resolved day identity, one line per day: the temporal cycle and the
+sanctoral calendar reconciled by the rite's own rules of precedence,
+occurrence, commemoration and transfer.
+.TP
+.BI readings " YEAR"
+The Mass reading citations, one line per day.
+.TP
+.BR \-h ", " \-\-help
+Print a usage summary to standard output and exit 0.
+.SH OUTPUT FORMAT
+.SS day
+.RS
+.nf
+date weekday season week slug rank colour [+commemoration ...]
+.fi
+.RE
+.PP
+Space\-separated, with one
+.BI + slug
+suffix per admitted commemoration. A
+.B \-
+in the week column means the day carries no week number.
+.RS
+.nf
+
+2026\-04\-05 sunday paschaltide 1 ef\-easter\-sunday class\-1 white
+2026\-11\-02 monday time\-after\-pentecost 23 commemoration\-of\-all\-souls class\-1 black
+2057\-03\-26 monday lent 3 annunciation\-of\-the\-blessed\-virgin\-mary class\-1 white +ef\-lent\-3\-monday
+.fi
+.RE
+.SS readings
+.RS
+.nf
+date slug | Epistle | Gospel
+.fi
+.RE
+.PP
+A reading citation contains spaces and commas, so this report separates its
+fields with
+.RB \(lq " | " \(rq
+where
+.B day
+stays space\-separated. That is the reason the citations are a separate command
+rather than extra columns on
+.BR day :
+appended there, no field number could recover where the Epistle ended. A
+.B \-
+in either citation field means none was resolved.
+.RS
+.nf
+
+2026\-12\-25 ef\-nativity | Heb 1:1\-12 | John 1:1\-14
+2038\-03\-06 sts\-felicitas\-perpetua | Ecclus 51:1\-8, 12 | Matt 13:44\-52
+.fi
+.RE
+.PP
+Both reports are one line per day and ordered by date, so they compose with
+.BR grep (1),
+.BR awk (1)
+and
+.BR join (1)
+in the ordinary way.
+.SH ENVIRONMENT
+.TP
+.B COLITUR_DATA_DIR
+Read the calendar data from this directory instead of the installed or
+build\-tree location. If it is set and contains no
+.IR sanctoral.sexp ,
+.B colitur
+exits 2 naming the directory; it does
+.I not
+fall back to another copy. Naming a directory states an intent, and quietly
+computing a calendar from different data than the one requested is a failure
+mode this program refuses.
+.SH FILES
+.TP
+.I <prefix>/share/colitur/ef/
+The installed calendar data: the sanctoral calendar, its one hand\-authored
+overlay, the temporal lectionary and the Commons. Four S\-expression files.
+.TP
+.I <exedir>/../data/ef/
+The build\-tree location, used when running from a source checkout.
+.PP
+Resolution order is
+.B COLITUR_DATA_DIR
+first, then the installed directory, then the build tree. A directory counts
+only if it actually contains
+.IR sanctoral.sexp ,
+so a failed or half\-removed installation falls through to a working checkout
+instead of shadowing it.
+.SH EXIT STATUS
+.TP
+.B 0
+Success.
+.TP
+.B 2
+Bad usage, a year outside 1583..9999, or the calendar data could not be read.
+.SH EXAMPLES
+Easter and its dependent feasts:
+.RS
+.nf
+
+.B colitur easter 2026
+.fi
+.RE
+.PP
+One date:
+.RS
+.nf
+
+.B colitur day 2026 | grep '^2026\-12\-25'
+.fi
+.RE
+.PP
+Every first\-class day of a year:
+.RS
+.nf
+
+.B colitur day 2026 | awk '$6 == "class\-1"'
+.fi
+.RE
+.PP
+Days carrying at least one commemoration:
+.RS
+.nf
+
+.B colitur day 2027 | grep '+'
+.fi
+.RE
+.PP
+Run against a checkout's data rather than the installed copy:
+.RS
+.nf
+
+.B COLITUR_DATA_DIR=~/git/projects/colitur/data/ef colitur day 2026
+.fi
+.RE
+.SH SOURCES
+The calendar is computed against the 1962
+.I Missale Romanum
+and its
+.IR "Rubricae Generales" ,
+which are the sole authority for what
+.B colitur
+emits. Published calendars \(em missalemeum, Divinum Officium, gcatholic \(em
+are used as comparison oracles in the test suite only: a divergence from one
+is flagged loudly and adjudicated against the Missal, never silently adopted.
+Several such divergences have been resolved in this engine's favour.
+.SH LIMITATIONS
+Only the Extraordinary Form (1962) is implemented; the Ordinary Form is a
+planned peer module, not an overlay of this one.
+.PP
+Only the Epistle and the Gospel are emitted. The chants \(em Psalm, Gradual,
+Tract, Alleluia, Sequence \(em are deliberately not computed: they have no
+source in this engine's data and no oracle to validate them against, and the
+engine rejects any citation part outside those two rather than emit one it
+cannot stand behind.
+.PP
+The votive Office of the Blessed Virgin Mary on Saturday is kept, but the
+seasonal selection among its five Masses is not yet implemented, so its
+reading citations fall back to the day's ordinary ones.
+.SH SEE ALSO
+.BR lectio (1)
+.SH LICENSE
+AGPL\-3.0\-or\-later.