docs(readme): strip unimplemented security claims, document actual state - #5

Summary

Rewrite the public README so it matches what the Rust binary actually does today. Pulled from the Sprint 1.5 deep audit of sigops-agent@main.

Removed (no code on main):

• Outbound WebSocket transport (agent uses HTTP long-polling)
• 8-layer security model (Layers 2 / 7 / 8 are not implemented)
• mTLS (no tls.rs, no cert handling)
• Signed command verification (no sha2 / ring in Cargo.toml)
• Namespace / cgroup sandbox (sandbox.rs does not exist)
• 24-hour token-rotation claim (rotation happens per-heartbeat, not per-24h)
• Installer URL get.sigops.dev/agent
• Docker image on GHCR
• pm2 / kubectl executor adapters
• Module-layout diagram showing ws/, tools/, discovery/, security/sandbox.rs, etc. (actual layout is flat: config.rs, discovery.rs, heartbeat.rs, executor.rs, security.rs, health.rs, main.rs, lib.rs)

Kept / clarified (verified in code):

• Command whitelist
• Path deny list
• Execution timeout with SIGKILL
• Token rotation on each heartbeat cycle
• Outbound-only HTTP (optional local /health on :9100, disablable with --no-health)
• 4+1 built-in tools (restart, http, notify_slack, wait, condition)
• 3-OS CI matrix (Ubuntu / macOS / Windows)

Added:

• ## Roadmap section listing the unshipped items above (WSS, mTLS, signed commands, sandbox, auto-update, installers, container image, code signing, cargo audit / SBOM)
• Transport section stating HTTP long-polling explicitly
• Configuration table with real env vars and CLI flags

Test plan

• Checked every bullet against the src/ tree
• Confirmed no ws/, no tls.rs, no sandbox.rs, no sha2/ring in Cargo.toml
• Reviewer confirms the roadmap captures every feature a customer might have expected from the old README

https://claude.ai/code/session_01VZPc4xQECHmaTddwaq6zf2