Add CLAUDE.md, project memory notes, and token_count

CLAUDE.md points future sessions at .claude/memory/ for accumulated
project context (purpose, SA/MR topology, packaging/signing decisions,
open external dependencies) not fully captured elsewhere in the repo.

.claude/memory/open-external-dependencies.md

@@ -0,0 +1,15 @@
+# Open External Dependencies
+
+Things the packaging/signing design assumes exist but doesn't own or
+fully specify — needed before implementation:
+
+- **FEC HTTP service** for the MR one-way hop — assumed already available,
+  ~1GB chunks, not built as part of this design.
+- **Existing S3 handover interface spec** — a separate, already-established
+  convention elsewhere in this environment for mapping S3 user object
+  metadata (`x-amz-meta-*` headers) to NiFi attributes via a regular
+  expression, plus a flag indicating whether the attribute set exceeded
+  S3's ~2KB metadata limit (in which case it falls back to this design's
+  JSON trailer). The exact regex pattern and flag/tag name are **not**
+  reproduced in the packaging/signing spec — need to source that document
+  before implementation.