regex: \p{...} property classes; interop: the String method surface (cuerdas is green)

\p{L}/\p{Lu}/\p{Ll}/\p{N}/\p{Z}/\p{Ps}/\p{Pe} (+\P negation) land in
both escape positions of the regex compiler, mapped onto the byte PEGs:
ASCII exact, any high byte (inside a UTF-8 sequence) counts as a LETTER —
so ^\p{L}+$ accepts UTF-8 words while \p{N}/\p{Z} stay ASCII. (?u) was
already a tolerated no-op flag. Unknown property names error at compile.

Chasing the acceptance target (cuerdas via deps-conformance) pulled in the
rest of its clj-compat chain, each a real gap:
- the deps-conformance harness reads libraries under clj-compat reader
  features (deps are clj/cljc by definition — without :clj, cuerdas's
  #?(:clj (instance? Pattern x)) branches resolved to NIL bodies)
- instance? knows Pattern/java.util.regex.Pattern (regex values) and
  Character (cuerdas's rx/regexp? gate on split)
- the java.lang.String method surface: .toLowerCase/.toUpperCase/.trim/
  .indexOf(-1 on miss)/.lastIndexOf/.substring/.charAt/.startsWith/
  .endsWith/.contains/.replace/.equalsIgnoreCase/... — ASCII case mapping,
  unknown methods error (the old path silently returned nil)
- the (.method obj args) SUGAR now desugars to (. obj method args) in the
  interpreter — it was never implemented (bare .method heads resolved as
  vars, hence 'Cannot call nil')
- Long/MAX_VALUE / MIN_VALUE statics (f64 approximations)

deps-conformance: medley ok, cuerdas ok (was check-error); dependency now
loads its clj branches and fails only on its single-segment ns resolution.
30 new spec rows (11 regex, 19 interop). Gate exit 0.

test/spec/regex-spec.janet

@@ -31,3 +31,19 @@
   ["split on regex"   "[\"a\" \"b\" \"c\"]" "(do (require '[clojure.string :as s]) (s/split \"a1b2c\" #\"\\d\"))"]
   ["replace regex"    "\"X-X\"" "(do (require '[clojure.string :as s]) (s/replace \"a-b\" #\"[a-z]\" \"X\"))"]
   ["replace $1"       "\"[a][b]\"" "(do (require '[clojure.string :as s]) (s/replace \"ab\" #\"([a-z])\" \"[$1]\"))"])
+
+# Unicode property classes (jolt-xlp), byte-PEG approximation: ASCII exact,
+# any high byte (inside a UTF-8 sequence) counts as a LETTER for \p{L}.
+# Acceptance target was cuerdas (kebab/snake/capital now pass conformance).
+(defspec "regex / \\p property classes"
+  ["p{L} ascii"      "\"hello\"" `(re-matches #"^\p{L}+$" "hello")`]
+  ["p{L} utf-8"      "true"      `(boolean (re-matches #"^\p{L}+$" "héllo"))`]
+  ["p{L} rejects digits" "false" `(boolean (re-matches #"^\p{L}+$" "ab1"))`]
+  ["p{N}"            "(quote (\"12\" \"345\"))" `(re-seq #"\p{N}+" "a12b345")`]
+  ["P{N} negation"   "\"abc\""   `(re-matches #"^\P{N}+$" "abc")`]
+  ["inside class"    "\"a-1_b\"" `(re-matches #"^[\p{N}\p{L}_-]+$" "a-1_b")`]
+  ["p{Lu}/p{Ll}"     "\"aB\""    `(re-matches #"^\p{Ll}\p{Lu}$" "aB")`]
+  ["p{Z} space"      "\"  \""    `(re-matches #"(?u)^[\s\p{Z}]+$" "  ")`]
+  ["p{Ps}/p{Pe}"     "\"(x)\""   `(re-matches #"^\p{Ps}x\p{Pe}$" "(x)")`]
+  ["(?u) accepted"   "\"hi\""    `(re-matches #"(?u)^hi$" "hi")`]
+  ["unknown class throws" :throws `(re-pattern "\p{Greek}")`])