Step 7d complete: exhaustive match checking + evaluator cleanup

Match exhaustiveness analysis:
- check-match-exhaustiveness function in evaluator.sx
- lint-node in tree-tools.sx checks match forms during format-check
- Warns on: no wildcard/catch-all, boolean missing true/false case
- (match x (true "yes")) → "match may be non-exhaustive"

Evaluator cleanup:
- Added missing step-sf-callcc definition (was in old transpiled output)
- Added missing step-sf-case definition (was in old transpiled output)
- Removed protocol functions from bootstrap skip set (they transpile fine)
- Retranspiled VM (bootstrap_vm.py) for compatibility

2650 tests pass (+5 from new features).

All Step 7 features complete:
  7a: ->> |> as-> pipe operators
  7b: Dict patterns, &rest, let-match destructuring
  7c: define-protocol, implement, satisfies?
  7d: Exhaustive match checking

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

lib/tree-tools.sx

@@ -1059,6 +1059,31 @@
                                     pname)))
                               (append! seen pname)))))
                       params))))))
+          (when
+            (= head-name "match")
+            (when
+              (>= (len node) 3)
+              (let
+                ((clauses (rest (rest node)))
+                  (patterns (map first clauses))
+                  (has-wildcard
+                    (some
+                      (fn
+                        (p)
+                        (and
+                          (symbol? p)
+                          (not (= (symbol-name p) "true"))
+                          (not (= (symbol-name p) "false"))))
+                      patterns))
+                  (has-else false))
+                (when
+                  (not has-wildcard)
+                  (append!
+                    warnings
+                    (str
+                      "WARN "
+                      (path-str path)
+                      ": match may be non-exhaustive (no catch-all pattern)"))))))
           (for-each
             (fn
               (i)