fix: add dist-check guard + List<T> type parsing + state machine examples

- check-dist.sh: Prevents DIST DESYNC by verifying all dist/*.js files
  are newer than their src/*.ts sources. Fails build if stale.
- Makefile: Standard build targets (build/check-dist/test/recompile/clean)
- src/index.ts: Integrated dist freshness check before compilation
- src/parser.ts: Added List<T> type parsing alongside existing Set<T>/Map<K,V>
  (e.g., 'log: List<LogEntry>' now parses as { type: 'list', elementType })
- examples/: Restored v0.3 state machine specs (TigerBeetleLedger,
  AccountLedger, ToggleSwitch, TwoPhaseCommit)
- DIST DESYNC is a known recurring anti-pattern — this guard prevents it

Tests: 39/41 pass (2 pre-existing E2E WASM failures due to missing wabt)

compiler/test-output/RetryHandler.specbom.cdx.json

@@ -38,7 +38,7 @@
         "name": "Scott Scoble",
         "email": "scott@scoble.me"
       },
-      "timestamp": "2026-05-03T20:13:42.867Z"
+      "timestamp": "2026-05-05T10:11:33.425Z"
     },
     {
       "subject": "speck:RetryHandler",
@@ -53,7 +53,7 @@
         "name": "Speckl Compiler",
         "email": "compiler@speckl.scoble.me"
       },
-      "timestamp": "2026-05-03T20:13:42.867Z"
+      "timestamp": "2026-05-05T10:11:33.425Z"
     },
     {
       "subject": "speck:RetryHandler",
@@ -68,7 +68,7 @@
         "name": "Speckl Compiler",
         "email": "compiler@speckl.scoble.me"
       },
-      "timestamp": "2026-05-03T20:13:42.867Z"
+      "timestamp": "2026-05-05T10:11:33.425Z"
     }
   ]
 }