v0.5.4 — delete agent-runner sidecar; auto-update + opt-in metrics

Highlights

~10,000 LOC net surface-shrink by deleting the agent-runner sidecar after recognizing it was vestigial post-plugin-extraction. Provider plugins (claude/codex/gemini/opencode) handle CLI invocation; animus agent run is reimplemented as a thin client over SessionBackendResolver.

Major changes

• agent-runner sidecar deleted. ~8000 LOC removed; animus agent {run,status,cancel,control} now dispatches directly to provider plugins via the existing plugin host. The Unix-socket bridge, runner_helpers supervisor, lockfile, and shared-secret auth are gone. The published animus-agent-runner-protocol crate is marked deprecated.
• animus runner restart-stats removed. No more sidecar to restart.
• DaemonHealth schema: new provider_plugins_healthy: bool field; legacy runner_connected/runner_pid kept for wire back-compat (always false/None).
• animus agent control returns unavailable (exit code 5) under the provider-only model.

Added

• animus self update — configurable auto-update with four modes (off / notify / prompt / auto), channel filtering (stable / prerelease), atomic same-directory binary swap. Env: ANIMUS_AUTO_UPDATE_MODE, ANIMUS_AUTO_UPDATE_DISABLE.
• animus metrics — opt-in anonymous event counters with first-run prompt. Hard opt-in; closed-enum events with bounded tag types; no code/paths/repos/prompts ever in the payload. Env kill-switch: ANIMUS_METRICS_DISABLE=1. Default endpoint is a placeholder pending product confirmation.
• system_prompt_file on AgentProfile — load the system prompt from an external UTF-8 file (resolved relative to source YAML). Inlined verbatim at compile time.
• HTTP MCP servers in workflow YAML — mcp_servers: entries can declare transport: http + url: so workflows can reach remote MCPs (e.g. Robinhood's hosted MCP) without bridge scripts.

Infrastructure

• Rust toolchain pinned to 1.96.0 via rust-toolchain.toml.

See CHANGELOG.md for the full diff.