feat: Add loading spinner and smart output visualization for UX

Implemented two major UX enhancements for aofctl:

1. Loading Spinner (#72)
   - Shows animated spinner while agent executes
   - Updates every 100ms with rotating animation
   - Automatically clears when execution completes
   - Clean visual feedback in non-interactive mode

2. Smart Output Visualization (#73)
   - Auto-detects output format (JSON, tables, lists, docker stats)
   - Beautiful Unicode table rendering with comfy-table
   - Colorized output with colored crate
   - Robust with graceful fallback to plain text
   - Never crashes on unexpected formats

Additional improvements:
   - Smart docker stats --no-stream injection
   - Clean error-level logging by default
   - Token efficiency documentation
   - Simplified getting-started example

Dependencies added:
   - comfy-table: 7.1 (table rendering)
   - colored: 2.1 (terminal colors)

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

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

Author: initcron

crates/aof-core/src/tool/structured_output.rs

@@ -21,7 +21,8 @@ observability = ["reqwest", "chrono"]
 cicd = ["reqwest", "chrono"]
 security = ["reqwest", "base64", "urlencoding"]
 cloud = []
-all = ["file", "shell", "kubectl", "docker", "git", "terraform", "http", "observability", "cicd", "security", "cloud"]
+benchmark = ["chrono", "rand"]
+all = ["file", "shell", "kubectl", "docker", "git", "terraform", "http", "observability", "cicd", "security", "cloud", "benchmark"]
 
 [dependencies]
 aof-core = { workspace = true }
@@ -37,6 +38,7 @@ chrono = { workspace = true, optional = true }
 which = { workspace = true }
 base64 = { version = "0.22", optional = true }
 urlencoding = { version = "2.1", optional = true }
+rand = { version = "0.8", optional = true }
 
 [dev-dependencies]
 tokio = { workspace = true, features = ["test-util", "full", "macros"] }