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, 28 insertions, 0 deletions

diff --git a/lib/render/escape.mli b/lib/render/escape.mli
new file mode 100644
index 0000000..97cf050
--- /dev/null
+++ b/lib/render/escape.mli
@@ -0,0 +1,28 @@
+(** Per-flavour escaping for the template engine, plus RFC 5545 line folding.
+
+    Knows nothing about calendars. Pure and total: every function is defined on
+    every string, and none reads the clock, the environment or the filesystem. *)
+
+(** The six escaping modes. Markdown, AsciiDoc and plain text all use [None_]:
+    their metacharacter sets are context-dependent, and escaping them
+    aggressively produces worse output than not escaping at all (spec section 5).
+    This is a documented limitation of those flavours. *)
+type flavour = Latex | Groff | Html | Xml | Ics | None_
+
+val all : flavour list
+val to_string : flavour -> string
+val of_string : string -> flavour option
+
+(** [of_extension ".tex"] is [Some Latex]. Returns [None] for an unrecognised
+    extension: the caller must treat that as an error, never as a fallback to
+    [None_] (spec section 5 -- guessing wrong here produces malformed output
+    that looks fine until it does not). *)
+val of_extension : string -> flavour option
+
+(** Escape one interpolated value for [flavour]. *)
+val apply : flavour -> string -> string
+
+(** Fold one unfolded content line per RFC 5545 section 3.1: at most 75 octets
+    per line, continuation lines prefixed with one space, CRLF terminators,
+    never splitting a UTF-8 sequence. The returned string ends with CRLF. *)
+val fold_ics : string -> string