feat(of): transfer_target per Normae nn. 5 and 60

Three rules, in priority order: the Annunciation in Holy Week goes to
Easter+8; any other solemnity on a Sunday of Advent, Lent or Easter goes to
the following Monday (n. 5, which n. 60 defers to explicitly), except on Palm
Sunday or Easter Sunday; otherwise the nearest later day free of Tabula
entries 1-8.

The n. 5 Monday rule is easy to miss -- n. 60 names it only by cross
reference, and reading n. 60 alone yields a single search rule where the
sources give three.

Shaped to match Rite.t.transfer_target so a later phase wires it unchanged,
with its own step bound: Calendar's round guard bounds rounds, not one call's
internal search.

2 files changed, 115 insertions, 0 deletions

diff --git a/lib/rites/rite_of/precedence_of.ml b/lib/rites/rite_of/precedence_of.ml
index 5d32ee2..2fab64d 100644
--- a/lib/rites/rite_of/precedence_of.ml
+++ b/lib/rites/rite_of/precedence_of.ml
@@ -254,3 +254,93 @@ let vigil_feast (_ : Vocab_of.rank Precedence.candidate) : Slug.t option = None
    together. *)
 let rules : (Vocab_of.season, Vocab_of.rank) Precedence.rules =
   { band; disposition; admit; vigil_feast }
+
+(* Normae n. 60 and Normae n. 5 together. THREE rules, in this priority order
+   -- n. 60's own text defers to n. 5 explicitly ("servatis iis quae n. 5
+   statuuntur"), so the two are one rule set, not two competing ones.
+
+   1. THE ANNUNCIATION IN HOLY WEEK (Normae n. 60): "Sollemnitas vero
+      Annuntiationis Domini, quotiescumque occurrit aliquo die Hebdomadae
+      sanctae, semper ad feriam II post dominicam II Paschae erit
+      transferenda." A fixed destination, Easter + 8, not a search. The EF has
+      the identical rule for the identical feast (RG 96's own exception, "the
+      Monday after Low Sunday" -- Low Sunday IS the Second Sunday of Easter),
+      which is why Rite.t.transfer_target is a rite-supplied function at all;
+      see its own doc comment.
+
+   2. A SOLEMNITY ON A PRIVILEGED SUNDAY (Normae n. 5): "Sollemnitates autem in
+      his dominicis occurrentes ad feriam secundam sequentem transferuntur" --
+      the FOLLOWING MONDAY, not a searched free day. "his dominicis" are n. 5's
+      own subject: the Sundays of Advent, Lent and Easter. The clause carries
+      its own exception -- "nisi agatur de occurrentia in Dominica in Palmis
+      aut in Dominica Resurrectionis Domini" -- and those two cases fall
+      through to rule 3, whose forward search handles them correctly (the
+      Monday after Palm Sunday is Tabula entry 2 and is therefore not free).
+
+   3. THE GENERAL RULE (Normae n. 60): "ad proximiorem diem transferatur qui
+      sit liber a diebus sub nn. 1-8 in tabula praecedentiae recensitis" --
+      the nearest later day free of Tabula entries 1-8, i.e. the first date
+      whose occupant bands ABOVE 80 (entry 8 x 10).
+
+   TERMINATION, which Rite.t.transfer_target requires the rite to guarantee:
+   the search is bounded at [max_search_days] steps and raises if exhausted.
+   That bound is STRUCTURAL -- it does not appeal to the real calendar's own
+   shape -- because Calendar's round guard bounds ROUNDS, not the internal
+   search of a single call, and an unbounded walk would hang the caller
+   outright before that guard was ever consulted. *)
+
+let max_search_days = 400
+
+let annunciation_slug = "of-annunciation"
+
+(* Tabula entries 1-8, scaled: a day is FREE to receive a transfer when its
+   occupant bands strictly above entry 8. *)
+let entry_8_band = 80
+
+let transfer_target (c : Vocab_of.rank Precedence.candidate) (origin : Date.t)
+    (occupant : Date.t -> Vocab_of.rank Celebration.t) : Date.t =
+  let year = Date.year origin in
+  let easter = Computus.gregorian_easter year in
+  let offset d = Date.to_rata d - Date.to_rata easter in
+  let is_holy_week d = offset d >= -7 && offset d <= -1 in
+  (* Rule 1. *)
+  if Slug.to_string c.cel.slug = annunciation_slug && is_holy_week origin then
+    Date.add_days easter 8
+  else
+    let season_of d = (Temporal_of.temporal d).Temporal.season in
+    let privileged_sunday d =
+      Date.weekday d = Date.Sun
+      && match season_of d with
+         | Vocab_of.Advent | Vocab_of.Lent | Vocab_of.Easter -> true
+         | Vocab_of.Christmas | Vocab_of.Ordinary_time -> false
+    in
+    let is_palm_sunday d = offset d = -7 in
+    let is_easter_sunday d = offset d = 0 in
+    (* Rule 2. *)
+    if
+      c.cel.rank = Vocab_of.Sollemnitas
+      && privileged_sunday origin
+      && (not (is_palm_sunday origin))
+      && not (is_easter_sunday origin)
+    then Date.add_days origin 1
+    else
+      (* Rule 3. *)
+      let free d =
+        let cel = occupant d in
+        let cand = { Precedence.cel; origin = Precedence.Temporal } in
+        let ctx =
+          { Precedence.date = d; season = season_of d; weekday = Date.weekday d }
+        in
+        band ctx cand > entry_8_band
+      in
+      let rec search d steps =
+        if steps > max_search_days then
+          failwith
+            (Printf.sprintf
+               "Precedence_of.transfer_target: no day free of Tabula entries \
+                1-8 within %d days of %s"
+               max_search_days (Date.to_iso8601 origin))
+        else if free d then d
+        else search (Date.add_days d 1) (steps + 1)
+      in
+      search (Date.add_days origin 1) 1
diff --git a/lib/rites/rite_of/precedence_of.mli b/lib/rites/rite_of/precedence_of.mli
index e81d35e..4822411 100644
--- a/lib/rites/rite_of/precedence_of.mli
+++ b/lib/rites/rite_of/precedence_of.mli
@@ -85,3 +85,28 @@ val vigil_feast : Vocab_of.rank Precedence.candidate -> Slug.t option
 
 (** The four functions assembled for {!Colitur_kernel.Precedence.resolve}. *)
 val rules : (Vocab_of.season, Vocab_of.rank) Precedence.rules
+
+(** [transfer_target c origin occupant]: where an impeded solemnity goes.
+    Normae n. 60 and Normae n. 5 together -- n. 60 defers to n. 5 explicitly
+    ("servatis iis quae n. 5 statuuntur"), so they are one rule set:
+
+    - the Annunciation falling anywhere in Holy Week goes to Easter + 8, the
+      Monday after the Second Sunday of Easter (n. 60, a fixed destination);
+    - any other solemnity falling on a Sunday of Advent, Lent or Easter goes to
+      the following Monday (n. 5), except on Palm Sunday or Easter Sunday,
+      which n. 5 excludes and which fall through to the general rule;
+    - otherwise, the nearest later day free of Tabula entries 1-8 (n. 60).
+
+    Shaped to match {!Colitur_kernel.Rite.t.transfer_target} exactly so a later
+    phase wires it with no adaptation, and honours both obligations that field
+    states: the result is strictly later than [origin], and the search carries
+    its own step bound rather than relying on {!Colitur_kernel.Calendar}'s
+    round guard, which bounds rounds rather than one call's internal search.
+
+    @raise Failure if no free day is found within 400 days -- a structural
+    bound, not an appeal to the calendar's own shape. *)
+val transfer_target :
+  Vocab_of.rank Precedence.candidate ->
+  Date.t ->
+  (Date.t -> Vocab_of.rank Celebration.t) ->
+  Date.t