fix: audit findings — parser strictness, name ambiguity, and errors

Found by auditing the shipped program rather than the diff.

The parser accepted OCaml integer-literal syntax, so "Luke 1_1:5" read as
chapter ELEVEN and "+5" as 5 -- a typo silently becoming a different
chapter, reachable through any user overlay. Numbers are now plain digits
and positive, and a descending range is rejected: 1:20-10 is always a
transcription error. No shipped citation changed.

FOUR PAIRS OF DIFFERENT BOOKS SHARED A FULL TITLE. 1 and 2 Corinthians
both rendered "Epistola ad Corinthios", as did Thessalonians, Timothy and
Peter -- 108 citations in 2027 alone that a reader cannot resolve to a
book. This is the Kings defect fixed earlier and not generalised. The
titles now carry their volume numeral, marked CONSTRUCTED, and a test
asserts no two books share a name -- while allowing the case where two
ids ARE the same book under different numbering, which a tradition
relates.

Spec section 8.5 is now delivered rather than merely recorded. Shipped
styles did not re-parse their own output: 32 of 52 Latin abbreviations
and 49 of 52 full titles failed, so a citation copied from colitur's own
output into an overlay was passed through untouched and printed in the
wrong language, silently. Every shipped name is registered as a spelling
and split_book learned multi-word titles by longest-token match. Now 0
of 52 fail beyond the same-book aliases.

Overlay errors were written for a compiler author: they named an OCaml
source file the reader does not have and buried the useful token. The
existing five-path rewriter is replaced by a generic one, applied to
every load path rather than one, so "rank: is not one of the allowed
values (at Class9)" replaces the raw Of_sexp_error dump.

Also: the new-overlay scaffold documented citations and layer without
showing them, and its comment implied the wrong nesting -- the single
easiest thing to get wrong; error messages echoed whole file lines,
copying an unrelated file's contents into stderr when a flag pointed at
one; and config --show validated partway down its table, exiting 2 after
writing five rows to stdout.

1 files changed, 28 insertions, 3 deletions

diff --git a/bin/main.ml b/bin/main.ml
index acf8859..b1d9cac 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -1942,6 +1942,20 @@ let lang_check path =
    it via [load_lang]). *)
 let config_show ~lang_flag ~template_flag ~format_flag ~overlays_flag ~sigla_style_flag ~sigla_book_flag
     ~sigla_tradition_flag config =
+  (* VALIDATE BEFORE PRINTING ANYTHING. A usage error used to surface
+     halfway down the table, so `config --show --sigla-book bogus` exited 2
+     having already written five rows to stdout -- a caller redirecting
+     stdout to a file got a truncated, plausible-looking report alongside a
+     non-zero status. Nothing is emitted now until every value is known good. *)
+  let sigla_book_check, _ =
+    Colitur_naming.Config.resolve ~flag:sigla_book_flag
+      ~config:(Colitur_naming.Config.sigla_book config) ~default:"abbr"
+  in
+  if sigla_book_check <> "full" && sigla_book_check <> "abbr" then begin
+    Printf.eprintf "colitur: unknown --sigla-book %S (want \"full\" or \"abbr\")\n"
+      sigla_book_check;
+    exit 2
+  end;
   let cpath = config_path () in
   Printf.printf "config file: %s (%s)\n" cpath
     (if cpath <> "" && Sys.file_exists cpath then "exists" else "not found");
@@ -1996,8 +2010,13 @@ let new_overlay_template =
 ; universal entry -- by naming its slug.
 ((id my-parish)
   (directives
-    ; A fixed-date local feast. `citations` and `layer` may be omitted: they
-    ; default to empty and to this overlay's own id.
+    ; A fixed-date local feast, with its own Mass readings.
+    ;
+    ; NOTE WHERE `citations` AND `layer` GO: inside `cel`, beside `rank` and
+    ; `colour` -- NOT beside `date`. Both may be omitted, defaulting to no
+    ; readings and to this overlay's own id. This example shows them in
+    ; place because the nesting is the single easiest thing to get wrong,
+    ; and getting it wrong is what `unknown field(s): citations` means.
     ((Add
        ((date (Fixed (month 5) (day 20)))
          (cel
@@ -2007,7 +2026,13 @@ let new_overlay_template =
              ; status: Feast | Commemoration_only
              ; colour: White | Red | Violet | Green | Black | Rose
              ; subject: Lord | Bvm | Saint | Temporal
-             (rank Class3) (status Feast) (colour White) (subject Saint)))))
+             (rank Class3) (status Feast) (colour White) (subject Saint)
+             ; part: First | Gospel. The reference is a citation, never
+             ; scripture text -- colitur ships no Bible.
+             (citations
+               (((part First) (reference "Wis 7:7-14"))
+                 ((part Gospel) (reference "Matt 5:13-19"))))
+             (layer my-parish)))))
      ; A MOVABLE feast: the first Sunday of October. `nth` may be negative to
      ; count from the end of the month (-1 is the last).
      (Add