feat(memory): add git-backed version control for dream memory files

- Add GitStore class wrapping dulwich for memory file versioning
- Auto-commit memory changes during Dream consolidation
- Add /dream-log and /dream-restore commands for history browsing
- Pass tracked_files as constructor param, generate .gitignore dynamically

nanobot/command/builtin.py

@@ -96,23 +96,86 @@ async def cmd_dream(ctx: CommandContext) -> OutboundMessage:
 
 
 async def cmd_dream_log(ctx: CommandContext) -> OutboundMessage:
-    """Show the Dream consolidation log."""
-    loop = ctx.loop
-    store = loop.consolidator.store
-    log = store.read_dream_log()
-    if not log:
-        # Check if Dream has ever processed anything
+    """Show what the last Dream changed.
+
+    Default: diff of the latest commit (HEAD~1 vs HEAD).
+    With /dream-log <sha>: diff of that specific commit.
+    """
+    store = ctx.loop.consolidator.store
+    git = store.git
+
+    if not git.is_initialized():
         if store.get_last_dream_cursor() == 0:
-            content = "Dream has not run yet."
+            msg = "Dream has not run yet."
         else:
-            content = "No dream log yet."
+            msg = "Git not initialized for memory files."
+        return OutboundMessage(
+            channel=ctx.msg.channel, chat_id=ctx.msg.chat_id,
+            content=msg, metadata={"render_as": "text"},
+        )
+
+    args = ctx.args.strip()
+
+    if args:
+        # Show diff of a specific commit
+        sha = args.split()[0]
+        result = git.show_commit_diff(sha)
+        if not result:
+            content = f"Commit `{sha}` not found."
+        else:
+            commit, diff = result
+            content = commit.format(diff)
     else:
-        content = f"## Dream Log\n\n{log}"
+        # Default: show the latest commit's diff
+        result = git.show_commit_diff(git.log(max_entries=1)[0].sha) if git.log(max_entries=1) else None
+        if result:
+            commit, diff = result
+            content = commit.format(diff)
+        else:
+            content = "No commits yet."
+
     return OutboundMessage(
-        channel=ctx.msg.channel,
-        chat_id=ctx.msg.chat_id,
-        content=content,
-        metadata={"render_as": "text"},
+        channel=ctx.msg.channel, chat_id=ctx.msg.chat_id,
+        content=content, metadata={"render_as": "text"},
+    )
+
+
+async def cmd_dream_restore(ctx: CommandContext) -> OutboundMessage:
+    """Restore memory files from a previous dream commit.
+
+    Usage:
+        /dream-restore          — list recent commits
+        /dream-restore <sha>    — revert a specific commit
+    """
+    store = ctx.loop.consolidator.store
+    git = store.git
+    if not git.is_initialized():
+        return OutboundMessage(
+            channel=ctx.msg.channel, chat_id=ctx.msg.chat_id,
+            content="Git not initialized for memory files.",
+        )
+
+    args = ctx.args.strip()
+    if not args:
+        # Show recent commits for the user to pick
+        commits = git.log(max_entries=10)
+        if not commits:
+            content = "No commits found."
+        else:
+            lines = ["## Recent Dream Commits\n", "Use `/dream-restore <sha>` to revert a commit.\n"]
+            for c in commits:
+                lines.append(f"- `{c.sha}` {c.message.splitlines()[0]} ({c.timestamp})")
+            content = "\n".join(lines)
+    else:
+        sha = args.split()[0]
+        new_sha = git.revert(sha)
+        if new_sha:
+            content = f"Reverted commit `{sha}` → new commit `{new_sha}`."
+        else:
+            content = f"Failed to revert commit `{sha}`. Check if the SHA is correct."
+    return OutboundMessage(
+        channel=ctx.msg.channel, chat_id=ctx.msg.chat_id,
+        content=content, metadata={"render_as": "text"},
     )
 
 
@@ -135,7 +198,8 @@ def build_help_text() -> str:
         "/restart — Restart the bot",
         "/status — Show bot status",
         "/dream — Manually trigger Dream consolidation",
-        "/dream-log — Show Dream consolidation log",
+        "/dream-log — Show what the last Dream changed",
+        "/dream-restore — Revert memory to a previous state",
         "/help — Show available commands",
     ]
     return "\n".join(lines)
@@ -150,4 +214,7 @@ def register_builtin_commands(router: CommandRouter) -> None:
     router.exact("/status", cmd_status)
     router.exact("/dream", cmd_dream)
     router.exact("/dream-log", cmd_dream_log)
+    router.prefix("/dream-log ", cmd_dream_log)
+    router.exact("/dream-restore", cmd_dream_restore)
+    router.prefix("/dream-restore ", cmd_dream_restore)
     router.exact("/help", cmd_help)