Add deterministic CAS tree objects

docs/architecture.md

@@ -90,8 +90,10 @@ Resource kinds:
 `geth-cas` is implemented locally first using BLAKE3 hashes and filesystem blob
 storage. Local pin/unpin metadata is tracked in SQLite and surfaced in
 `cas list`. `cas cleanup` removes unpinned local blobs while retaining pinned
-blobs. Iroh-blobs, providers, encrypted blobs, richer cache policies, manifests,
-and file sync trees are future work.
+blobs. The CAS crate can build deterministic tree objects that describe
+directories, files, executable bits, and file blob hashes; those tree objects
+are stored as CAS blobs. Iroh-blobs, providers, encrypted blobs, richer cache
+policies, file roots, and sync conflict handling are future work.
 
 `geth-db` currently registers local SQLite paths as DB resources and reports
 local-only sync status plus a read-only SQLite schema summary/hash. It also

docs/roadmap.md

@@ -344,11 +344,12 @@ Automerge documents.
 Goal: build higher-level local-first collaboration on CAS trees, resource auth,
 and future group key evolution.
 
-- `[ ]` CAS tree objects.
+- `[x]` CAS tree objects.
   Acceptance criteria:
-  - Tree objects describe directories, files, executable bits, and blob hashes.
-  - Tree objects are content-addressed and stored in CAS.
-  - Tests cover deterministic tree hashing.
+  - `[x]` Tree objects describe directories, files, executable bits, and blob
+    hashes.
+  - `[x]` Tree objects are content-addressed and stored in CAS.
+  - `[x]` Tests cover deterministic tree hashing.
 
 - `[ ]` File roots.
   Acceptance criteria: