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/skills/jolt-gotchas/SKILL.md

@@ -0,0 +1,45 @@
+---
+name: jolt-gotchas
+description: Common pitfalls and workarounds discovered during Jolt implementation
+---
+
+# jolt-gotchas
+
+Recurring pitfalls and their fixes discovered across all implementation phases.
+
+## PHM/Set Metadata Key Leakage
+
+PHM and set internal keys (`:jolt/deftype`, `:cnt`, `:buckets`, `:_meta`, `:jolt/type`, `:phm`) leak into `pairs`/`keys` iteration. Must filter in merge, merge-with, keys, vals, and print-collection.
+
+```janet
+(when (and (not= k :jolt/deftype) (not= k :cnt) 
+           (not= k :buckets) (not= k :_meta)
+           (not= k :jolt/type) (not= k :phm)) ...)
+```
+
+## Keywords with `#` Are Invalid Janet Literals
+
+`:#inst`, `:#uuid` cause parse errors. Use dynamic table construction:
+```janet
+(let [dr @{}] (put dr (keyword "#inst") fn) dr)
+```
+
+## Janet `break` Only Works in Loops
+
+Does NOT work inside `let`. Use `(var found nil)` + `(set found val) (break)` pattern.
+
+## Bare Tuples in `eval` Are Function Calls
+
+`(eval [1 2 3])` calls `1` as function. Use `['tuple 1 2 3]` in data-structure emitter.
+
+## Janet `case` for Multi-Arity
+
+Janet lacks Clojure-style multi-arity defn. Use `(defn f [& args] (case (length args) 1 ... 2 ...))`.
+
+## core-renames + core-fn-values Must Stay in Sync
+
+Both tables must be updated together when adding core fns. Missing entries = silent nil returns. `"-"` is `core-sub` NOT `core--`.
+
+## `set!` Field Mutation Reader Quirk
+
+`(set! (.-x obj) val)` parses as array with `.-x` symbol head — not as standalone `.-x` symbol. Check for this case before the `(. obj -field)` shorthand.