Add bd info command to show database path and daemon status

Implements bd-145. Users can now easily determine which database file bd is using
and check daemon connection status.

Features:
- Shows absolute database path
- Displays daemon status (connected/mode/health/version)
- Shows issue count
- Supports --json output for programmatic use
- Works in both daemon and direct modes

Example output:
  bd info                    # Human-readable
  bd info --json             # JSON for agents
  bd info --no-daemon        # Force direct mode

Updated documentation in README.md and AGENTS.md.

Amp-Thread-ID: https://ampcode.com/threads/T-a33c0762-f800-4fea-9510-6a803d8aece8
Co-authored-by: Amp <amp@ampcode.com>

AGENTS.md

@@ -110,6 +110,9 @@ If you must use separate MCP servers:
 If you're not using the MCP server, here are the CLI commands:
 
 ```bash
+# Check database path and daemon status
+bd info --json
+
 # Find ready work (no blockers)
 bd ready --json