feat(fls): ZIP layer of the .fls codec

Reader and writer ported from filius-ipad with the same path policy,
limits and error codes; DEFLATE via fflate, cut at the declared size
like Apple Compression. 54 tests: the Swift archive rejection tests,
DEFLATE edge cases, and all 23 corpus files cross-checked against
fflate.unzipSync and round-tripped.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/fls/test/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "noEmit": true,
+    "composite": false,
+    "declaration": false,
+    "types": ["node"]
+  },
+  "include": ["."]
+}