feat(lang): traditions.ini, and its install rule

Which book a reference denotes does not vary by language, so it lives in
its own file rather than in la.ini beside [weekday].

Six mappings, not four: Osee/Jonas are the same question as 3 Kings in
transliteration form.

The install rule is added in the same commit deliberately -- lang/ once
shipped without one, so the feature worked from the source tree and was
broken once installed.

bin/dune gains colitur_citation as a linked library, needed for the new
loader; lang_list's directory scan now excludes traditions.ini, which is
not a language file and does not parse as one.

2 files changed, 78 insertions, 3 deletions

diff --git a/bin/dune b/bin/dune
index 28c04d7..0702a84 100644
--- a/bin/dune
+++ b/bin/dune
@@ -6,4 +6,9 @@
  ; colitur.opam's frozen depends, only a new library this executable links
  ; against. Used by Task 12's [mkdir_p] (colitur publish, recursive
  ; directory creation) and nowhere else.
- (libraries colitur_kernel rite_ef colitur_render colitur_naming unix))
+ ;
+ ; [colitur_citation] backs [load_tradition]'s own reading of
+ ; lang/traditions.ini (which book a reference DENOTES, {!Colitur_citation.Book}) --
+ ; a sibling library to [colitur_naming] (what a book is CALLED), not a
+ ; replacement for it.
+ (libraries colitur_kernel rite_ef colitur_render colitur_naming colitur_citation unix))
diff --git a/bin/main.ml b/bin/main.ml
index cf6cb33..5c9f342 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -641,6 +641,67 @@ let load_lang ~raw ~flag ~config =
                     | Error _ -> t
                     | Ok base -> Colitur_naming.Lang.with_fallback t base))))
 
+(* lang/traditions.ini answers a different question from la.ini/en.ini's own
+   [\[bible\]] section: which book a reference DENOTES, not what it is
+   CALLED. Naming varies by language (a [\[bible\]] section per language
+   file); denoting does not -- "modern numbering" is the same decision in
+   Latin, Polish and English -- so it gets its own file, read once here
+   rather than duplicated per language.
+
+   Reuses {!lang_dir} rather than adding a second probe: a tradition file
+   must resolve the same way a language file does, or an installed binary
+   could find one and not the other. Note carefully what that reuse implies
+   -- [lang_dir]'s own installed-vs-source-tree choice is gated on [la.ini]
+   existing, so it can legitimately return a directory that HAS [la.ini] but
+   NOT [traditions.ini] (an older install upgraded in place, from before
+   this file shipped). That case, like an unknown [name] naming no section
+   in the file, degrades to {!Colitur_citation.Book.vulgate} with a WARNING
+   on stderr -- never fatal. This deliberately does NOT mirror [load_lang]'s
+   own PRIMARY-file behaviour (a missing/unparsing la.ini is fatal, [exit 2])
+   -- it mirrors [load_lang]'s own FALLBACK-chain behaviour just above,
+   which already degrades silently rather than taking a good language table
+   down over a defect in a file it merely NAMES. Asking for a renumbering is
+   optional the way asking for a language is not: a run should not be lost
+   over a typo in [--sigla-tradition] (wired in Task 8) the way it is lost
+   over a typo in [--lang].
+
+   [name = "vulgate"] takes no shortcut around the file: [\[vulgate\]] is
+   shipped as a deliberately empty section (see traditions.ini's own
+   comment), and an empty field list is exactly {!Colitur_citation.Book.vulgate}
+   ([[]]) via the same {!Colitur_citation.Book.tradition_of_fields} path
+   every other tradition uses -- one code path, not a special case for the
+   default.
+
+   Not called from anywhere in this file yet: citations reach output at
+   exactly two places, [View.citation_ref] and [part_ref] below, and
+   threading [Sigla.t] (which this feeds) through both is a dedicated task
+   on its own, deliberately not done here alongside the loader. [-32] is
+   silenced for exactly that reason -- this is a complete, correct,
+   ready-to-call function with no caller yet, not dead code. *)
+let[@warning "-32"] load_tradition name =
+  let path = Filename.concat (lang_dir ()) "traditions.ini" in
+  let vulgate () = Colitur_citation.Book.vulgate in
+  match read_file path with
+  | Error _ ->
+      Printf.eprintf "colitur: no %s; tradition %S falls back to the Vulgate\n" path name;
+      vulgate ()
+  | Ok text -> (
+      match Colitur_kernel.Overlay_ini.parse_sections text with
+      | Error e ->
+          Printf.eprintf "colitur: %s: %s; tradition %S falls back to the Vulgate\n" path e name;
+          vulgate ()
+      | Ok sections -> (
+          match List.find_opt (fun (s : Colitur_kernel.Overlay_ini.section) -> s.name = name) sections with
+          | None ->
+              Printf.eprintf "colitur: %s: no tradition %S; falling back to the Vulgate\n" path name;
+              vulgate ()
+          | Some sec ->
+              List.iter
+                (fun k ->
+                  Printf.eprintf "colitur: %s: [%s]: unknown book %S (ignored)\n" path name k)
+                (Colitur_citation.Book.unknown_fields sec.fields);
+              Colitur_citation.Book.tradition_of_fields sec.fields))
+
 let extension path =
   match String.rindex_opt path '.' with
   | Some i -> String.sub path i (String.length path - i)
@@ -1514,7 +1575,16 @@ let convert_report path =
    [lang_dir ()], the same probe [load_lang] itself uses. Each is opened and
    parsed (not merely listed by filename) so a malformed file is flagged
    here rather than only failing later when someone actually tries to use
-   it. *)
+   it.
+
+   [traditions.ini] lives in the same directory but is not a language file
+   -- it answers which book a reference DENOTES, not what it is CALLED (see
+   [load_tradition] above) -- and does not even parse as one ([Lang.of_string]
+   requires its own [\[meta\]] section, which traditions.ini has no reason to
+   carry). Without this exclusion it would list here as "(unreadable: ...)",
+   which is not a defect in the file, only a mismatch between what this scan
+   assumes every [.ini] in the directory is and what is actually shipped
+   there now. *)
 let lang_list () =
   let dir = lang_dir () in
   match Sys.readdir dir with
@@ -1525,7 +1595,7 @@ let lang_list () =
       Array.sort compare files;
       Array.iter
         (fun f ->
-          if Filename.check_suffix f ".ini" then begin
+          if Filename.check_suffix f ".ini" && f <> "traditions.ini" then begin
             let code = Filename.remove_extension f in
             match read_file (Filename.concat dir f) with
             | Ok t -> (