Make the vault's git history optional

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

docs/Architecture.md

@@ -435,7 +435,7 @@ build artifacts, and the contents of a previous task's workspace.
 
 **How memory is used.**
 - **Everything read is snapshotted into the transcript** with its provenance
-  (document, revision, when retrieved), once per work item at first use.
+  (source, its revision or a hash of its content, when retrieved), once per work item at first use.
 - **Memory is a cache, never authority.** An agent may rely on it to know what
   exists and where to look; facts an action depends on are re-checked against the
   live system immediately before the action (preconditions, O2). When a proposal
@@ -611,9 +611,12 @@ tags), so the operator browses it in Obsidian with links, backlinks and the grap
 - **Writes are atomic** (write, then rename), so a reader never sees half a note.
 - **Access is through control tools** (L13): the harness reads and writes the mounted
   folders. No tool VM ever sees the vault.
-- **History:** the vault is a git repository on the agent host, and the harness
-  commits each write with the agent and work item that made it. A note's revision is
-  its commit (L6).
+- **Provenance is in the note itself:** the harness records the source, work item
+  and time of each write (L6), whatever else is kept.
+- **History is optional:** the harness may keep the vault as a git repository on the
+  agent host, committing each write with the agent and work item that made it. It
+  shows what an edit replaced; recovery doesn't depend on it (the host's snapshots
+  cover that, X4).
 
 **The operator's copy.** Syncthing keeps a copy on the operator's devices, with the
 direction set per folder:
@@ -621,7 +624,8 @@ direction set per folder:
   operator reads them, and a local edit never flows back;
 - **folders the operator writes** are receive-only on the host.
 
-So conflicts can't arise. Obsidian's own settings folder and `.git` are not synced.
+So conflicts can't arise. Obsidian's own settings folder (and `.git`, if kept) are
+not synced.
 
 **Never an instruction channel, never an approval channel.** Work is never read
 out of the vault, and an agent never writes there to make another agent act.