feat: output, rendering and publishing

Gives colitur a publishable exit. Until now its only output was terminal
rows; it can now print an ordo booklet and a wall calendar, publish an
iCalendar feed people subscribe to, and serve a static JSON/XML API.

  lib/render   escaping (six flavours + RFC 5545 folding), a deliberately
               logic-less template engine, the view model, and five
               emitters (CSV, JSON, XML, iCalendar, S-expression)
  CLI          emit, table, render, publish -- all accepting --overlay
  templates    ordo booklet in six flavours, wall grid in three
  schema       day-v1.json and colitur-v1.xsd, the published contract
  man          colitur-templates.5, plus colitur.1 updates

The view model is why the engine can stay logic-less: a month grid needs
leading blank cells, week bucketing and an in-month test, and a
logic-less template can compute none of it. Shaping the data in OCaml
keeps the engine safe for untrusted templates and makes the grid
trivial.

Formats split by whether correctness is mechanical. Presentation goes
through templates; iCalendar and XML get dedicated emitters, because
folding, exclusive DTEND, stable UIDs and schema fidelity are rules a
template cannot enforce and each fails silently in a subscriber's
client rather than loudly at generation.

publish is deterministic and non-destructive: two runs produce a
byte-identical tree, and --prune removes only files a previous run
created, refusing any manifest entry that escapes the output directory.

No new dependencies. The kernel and rite modules are untouched, and
colitur day and colitur readings remain byte-identical.

1 files changed, 37 insertions, 0 deletions

diff --git a/lib/render/template.mli b/lib/render/template.mli
new file mode 100644
index 0000000..4118496
--- /dev/null
+++ b/lib/render/template.mli
@@ -0,0 +1,37 @@
+(** A deliberately logic-less template engine (spec section 5).
+
+    A template is DATA, never a program: placeholders, sections, inverted
+    sections and comments, and nothing else. There are no partials, no lambdas,
+    no expression evaluation, no arithmetic, and no filesystem or process
+    access. There is deliberately no "raw" or triple-brace form -- a template
+    cannot opt out of its flavour's escaping.
+
+    Anything a calendar needs that this cannot express (a month grid's leading
+    blanks, week bucketing) is computed in {!View} and handed in as data. That
+    division is the design, not a workaround. *)
+
+(** What a template can be rendered against. *)
+type value =
+  | Str of string
+  | Bool of bool
+  | List of value list
+  | Obj of (string * value) list
+
+type node =
+  | Text of string
+  | Var of string list  (** dotted path, e.g. ["name"; "la"] *)
+  | Section of string list * node list
+  | Inverted of string list * node list
+
+(** Never raises; a malformed template is an [Error] with a human-readable
+    reason, because the template is user input. *)
+val parse : string -> (node list, string) result
+
+(** Render against a value. Escaping is applied to every interpolated value and
+    NEVER to the template's own literal text, which is the author's markup.
+    A missing key renders as the empty string -- the one deliberate silence, so
+    that a template survives a rite that does not set every optional field. *)
+val render : flavour:Escape.flavour -> node list -> value -> string
+
+(** [parse] then [render]. *)
+val render_string : flavour:Escape.flavour -> string -> value -> (string, string) result