Add -d/--detach flag for background daemon mode

[ReSyncc]

Problem

OpenFang is an autonomous agent OS — it should run as a background service without requiring a dedicated terminal session. Currently, openfang start blocks the terminal and the daemon dies when the terminal is closed. Users have to manually background it with nohup or &, which is a poor experience for an always-on system.

This contradicts the core design: agents, channels (Telegram, Discord, etc.), scheduled jobs, and workflows should keep running independently of any terminal session.

Solution

• openfang start now spawns the daemon in the background using the existing start_daemon_background() function (which was already used by openfang dashboard but not exposed to users) and returns immediately, printing the API URL and dashboard link
• openfang start when a daemon is already running now reports the existing daemon's URL instead of erroring out
• openfang start --foreground preserves the old blocking behavior for Docker containers and debugging
• Dockerfile updated to CMD ["start", "--foreground"] since containers need the foreground process to stay alive

Benefits

• Users can run openfang start and close their terminal — the daemon keeps running
• Agents stay active, channels remain connected, scheduled jobs continue executing
• No more confusing "already running" errors — idempotent start behavior
• Docker still works correctly with explicit --foreground
• Aligns CLI behavior with what users expect from a daemon/service command

Test plan

• cargo build -p openfang-cli compiles
• openfang start returns immediately, daemon accessible at printed URL
• openfang start again prints "already running" with URL
• openfang start --foreground blocks as before
• openfang stop stops the background daemon
• Docker container stays alive with start --foreground

🤖 Generated with Claude Code

[jaberjaber23]

Breaking behavior change that needs more work:

1. --config / -c is not forwarded to the background process. If a user runs openfang start -c /custom/config.toml, the background process starts with default config, not the custom one.

2. Exit code contract change — "already running" changed from exit(1) to success return. Scripts checking exit codes will break silently.

3. This is a breaking change for every user, tutorial, and script that uses openfang start expecting foreground behavior. Needs discussion and a deprecation warning at minimum.

4. Test plan items are unchecked — the PR was not actually tested.

[ReSyncc]

Breaking behavior change that needs more work:

1. `--config` / `-c` is not forwarded to the background process. If a user runs `openfang start -c /custom/config.toml`, the background process starts with default config, not the custom one.

2. Exit code contract change — "already running" changed from exit(1) to success return. Scripts checking exit codes will break silently.

3. This is a breaking change for every user, tutorial, and script that uses `openfang start` expecting foreground behavior. Needs discussion and a deprecation warning at minimum.

4. Test plan items are unchecked — the PR was not actually tested.

Great point, ended up going to a -d command style similar to detach apart of docker run and docker compose to avoid breaking behavior.

• openfang start remains foreground (no breaking change)
• --config and --yolo flags forwarded to the background process
• "Already running" keeps exit(1) (preserves script behavior)
• Fixed all callers of start_daemon_background() (main.rs, init_wizard.rs, cmd_dashboard)
• Updated docs/cli-reference.md with new flag, examples, and output for both modes
• Added comment to openfang start in README.md
• Added tip apart of openfang start command to let users know there is a -d arg to detach.

[ReSyncc]

• Daemon stdout/stderr redirected to ~/.openfang/daemon.log (append mode) instead of /dev/null
• Unix: setsid() via pre_exec hook so daemon survives terminal close
• libc added as Unix-only dependency for setsid
• Detach success output now shows log file path
• Timeout error message points user to daemon.log for debugging
• Falls back to /dev/null if log file can't be opened