Phase 8: Protocol System — defprotocol, extend-type, extend-protocol, satisfies?

- types.janet: type-registry, register-protocol-method, find-protocol-method, type-satisfies?
- core.janet: rewritten protocol macros (defprotocol, extend-type, extend-protocol, reify)
  Protocol value stores :jolt/type :jolt/protocol with :methods map
  Method dispatch fns use fn* [this & rest-args] → protocol-dispatch special form
- evaluator.janet: protocol-dispatch, register-method, make-reified special forms
  satisfies? special form with type registry lookup
  special-symbol? entries for all 3 protocol ops + satisfies?
- 4 test sections (35-38): defprotocol, extend-type, extend-protocol, satisfies?
  extend-type: basic dispatch works (42 constant), .-field accessor needs further debug
  satisfies?: fully functional with type registry
- 315 ok, 2 fail (pre-existing, unchanged)

.dirge/memory/PITFALLS.md

@@ -1,7 +1,7 @@
-Janet break can't be used inside let blocks — break returns from the innermost loop, and in a let, there's no loop. Pattern: use (var found nil) + (while ... (if condition (do (set found val) (break)))) then check found after loop.
+Janet `break` does NOT work inside `let` — it only breaks from loops (`while`, `loop`). When searching for a key in a bucket and needing to return a value, use `(var found nil)` + `(set found val) (break)` pattern then check `found` after the loop. Same for `break nil` in bucket-dissoc: capture index in a var, break, then construct result after loop.
 §
-core-binding macro: use array-map (plain struct) NOT hash-map/PHM for the binding frame. PHM's phm-get doesn't work with push-thread-bindings' var-get lookup. Symptom: "error: dynamic binding" with no useful message. Fix: emit (array-map [var sym] val ...) instead of (hash-map ...).
+Keywords containing `#` (like `:#inst`, `:#uuid`) are invalid Janet literal syntax. Use dynamic table construction: `(let [dr @{}] (put dr (keyword "#inst") fn) dr)` instead of `@{:#inst fn}`. This hit us in types.janet make-ctx :data-readers initialization.
 §
-Janet `and` returns the last truthy value (not boolean true). `(and (table? x) (get x :jolt/deftype))` returns the deftype string, which is truthy but not `true`. Wrap with `(if (and ...) true false)` when the return value must be a boolean. This hit core-map? and would hit any predicate returning the result of `and`.
+PHM/Set internal metadata keys (`:jolt/deftype`, `:cnt`, `:buckets`, `:_meta`, `:jolt/type`, `:phm`) leak into `pairs`/`keys` iteration. Must filter them in core fns like merge, merge-with, keys, vals, and in print-rendering code. `core-merge` without filtering produced corrupted PHMs with metadata as entries. Commit `9c44021` fixed this for merge; `c366963` for print-value.
 §
-set! field mutation: `(set! (.-x obj) val)` is read as `(set! (. -x obj) val)` — the target is an array with `.` as head. Check for this case BEFORE the existing `(.-field obj)` shorthand check (which is just `(. obj -field)`). The reader transforms `.`-prefixed symbols differently than expected: `.-x` becomes a symbol `-x` inside a `(. -x obj)` array form, NOT a standalone `.-x` symbol.
+Janet's `case` for multi-arity dispatch: `(defn f [& args] (case (length args) 1 ... 2 ...))`. Used in core-derive, core-isa?, core-ancestors, core-descendants because Janet doesn't support Clojure-style `([arg1] body1) ([arg1 arg2] body2)` multi-arity defn syntax.