Add one-line comments to all defines in 5 spec files

parser.sx (3), render.sx (15), harness.sx (21), signals.sx (23),
canonical.sx (12) — 74 comments total. Each define now has a ;;
comment explaining its purpose.

Combined with the evaluator.sx commit, all 215 defines across 6 spec
files are now documented. primitives.sx and special-forms.sx already
had :doc fields.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

spec/canonical.sx

@@ -1,3 +1,4 @@
+;; Deterministic serialization for content addressing
 (define
   canonical-serialize
   :effects ()
@@ -23,6 +24,7 @@
       (canonical-dict val)
       :else (str val))))
 
+;; Normalize number representation (no trailing zeros)
 (define
   canonical-number
   :effects ()
@@ -40,6 +42,7 @@
             (if (ends-with? trimmed ".") (str trimmed "0") trimmed))
           s)))))
 
+;; Serialize dict with sorted keys
 (define
   canonical-dict
   :effects ()
@@ -61,16 +64,19 @@
             sorted-keys))
         "}"))))
 
+;; Compute SHA3-256 content ID from an expression
 (define
   content-id
   :effects ()
   (fn (expr) (sha3-256 (canonical-serialize expr))))
 
+;; First 16 chars of content ID (short form)
 (define
   content-id-short
   :effects ()
   (fn (expr) (slice (content-id expr) 0 16)))
 
+;; Create a bytecode module container
 (define
   make-bytecode-module
   :effects ()
@@ -78,6 +84,7 @@
     (version source-hash code)
     (list (quote sxbc) version source-hash code)))
 
+;; Type predicate for bytecode modules
 (define
   bytecode-module?
   :effects ()
@@ -85,12 +92,16 @@
     (expr)
     (and (list? expr) (>= (len expr) 4) (= (first expr) (quote sxbc)))))
 
+;; Get module format version
 (define bytecode-module-version :effects () (fn (m) (nth m 1)))
 
+;; Get source content hash
 (define bytecode-module-source-hash :effects () (fn (m) (nth m 2)))
 
+;; Get compiled bytecode
 (define bytecode-module-code :effects () (fn (m) (nth m 3)))
 
+;; Create a code object (arity + constants + bytecode)
 (define
   make-code-object
   :effects ()
@@ -104,6 +115,7 @@
         (set! parts (concat parts (list :upvalue-count upvalue-count))))
       (concat parts (list :bytecode bytecode :constants constants)))))
 
+;; Create provenance record (author, timestamp, source)
 (define
   make-provenance
   :effects ()