fix: MCP init tool creates .beads in current directory

Critical bug: MCP init tool reported success but didn't create .beads
directory. It was using --db flag which tells bd to use an existing
database elsewhere instead of creating a new one.

Root cause:
- bd_client.init() was calling _global_flags() which adds --db flag
- bd init --db <path> uses existing db instead of creating new one
- Result: init appeared to succeed but created nothing

Fix:
- Remove _global_flags() from init command
- Only pass --actor flag (safe for init)
- Do NOT pass --db flag to init (defeats the purpose)
- Add explicit comment explaining why

Testing:
- Added test_init_creates_beads_directory() integration test
- Verifies .beads directory is created in current working directory
- Verifies database file has correct prefix
- All 91 tests pass

This was causing silent failures where agents thought they initialized
bd but the .beads directory was never created.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

integrations/beads-mcp/src/beads_mcp/bd_client.py

@@ -462,7 +462,11 @@ class BdClient:
         if params.prefix:
             cmd.extend(["--prefix", params.prefix])
 
-        cmd.extend(self._global_flags())
+        # NOTE: Do NOT add --db flag for init!
+        # init creates a NEW database in the current directory.
+        # Only add actor-related flags.
+        if self.actor:
+            cmd.extend(["--actor", self.actor])
 
         try:
             process = await asyncio.create_subprocess_exec(