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/integration/deps-conformance-test.janet

@@ -7,6 +7,11 @@
 (use ../../src/jolt/api)
 (use ../../src/jolt/types)
 (import ../../src/jolt/deps :as deps)
+(use ../../src/jolt/reader)
+# deps are clj/cljc libraries by definition (the jolt-dw4 premise): read them
+# under clj-compat features so their #?(:clj ...) branches resolve (spec
+# 02-reader S18 — features are a property of the loading context).
+(reader-features-set! ["jolt" "clj" "default"])
 
 (unless (os/getenv "JOLT_CONFORMANCE")
   (print "deps-conformance: set JOLT_CONFORMANCE=1 to run (needs network) — skipped")