feat(render): CSV and JSON emitters, and the published contract

Both consume the VIEW, not the kernel, so every emitter and every
template describe exactly the same fields -- there is one vocabulary,
not five.

CSV is RFC 4180: a field with a comma is quoted. That is live on real
data, not hypothetical -- 'St. Joseph, Spouse of the Bl. Virgin Mary'
would otherwise split into two columns.

JSON is hand-rolled because the dependency list is frozen and escaping
is the only subtlety. Control characters below 0x20 are \u-escaped per
RFC 8259 section 7.

There are no numbers in the view, deliberately: a consumer never has to
guess whether week is 2 or "2".

schema/day-v1.json pins the shape. Once a phone subscribes or a site
fetches this, it is a promise to strangers -- adding a field is minor,
renaming one means /v2/.

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/render/emit_json.ml b/lib/render/emit_json.ml
new file mode 100644
index 0000000..272e4ca
--- /dev/null
+++ b/lib/render/emit_json.ml
@@ -0,0 +1,47 @@
+(* emit_json.ml *)
+module T = Template
+
+let escape_string s =
+  let b = Buffer.create (String.length s + 8) in
+  Buffer.add_char b '"';
+  String.iter
+    (fun c ->
+      match c with
+      | '"' -> Buffer.add_string b "\\\""
+      | '\\' -> Buffer.add_string b "\\\\"
+      | '\n' -> Buffer.add_string b "\\n"
+      | '\r' -> Buffer.add_string b "\\r"
+      | '\t' -> Buffer.add_string b "\\t"
+      | c when Char.code c < 0x20 -> Buffer.add_string b (Printf.sprintf "\\u%04x" (Char.code c))
+      | c -> Buffer.add_char b c)
+    s;
+  Buffer.add_char b '"';
+  Buffer.contents b
+
+(* Emit the view tree directly. Bools stay bools; everything else is a string,
+   an array or an object -- there are no numbers in the view, deliberately, so a
+   consumer never has to guess whether "week" is 2 or "2". *)
+let rec write b (v : T.value) =
+  match v with
+  | T.Str s -> Buffer.add_string b (escape_string s)
+  | T.Bool x -> Buffer.add_string b (if x then "true" else "false")
+  | T.List l ->
+      Buffer.add_char b '[';
+      List.iteri (fun i x -> if i > 0 then Buffer.add_char b ','; write b x) l;
+      Buffer.add_char b ']'
+  | T.Obj kvs ->
+      Buffer.add_char b '{';
+      List.iteri
+        (fun i (k, x) ->
+          if i > 0 then Buffer.add_char b ',';
+          Buffer.add_string b (escape_string k);
+          Buffer.add_char b ':';
+          write b x)
+        kvs;
+      Buffer.add_char b '}'
+
+let year v =
+  let b = Buffer.create (64 * 1024) in
+  write b v;
+  Buffer.add_char b '\n';
+  Buffer.contents b