feat: Add ACP (Agent Client Protocol) job mode for delegating to any compatible coding agent (#1600)

* feat: add ACP (Agent Client Protocol) job mode for delegating to any compatible coding agent

Add a third container job mode (`JobMode::Acp`) that spawns any
ACP-compliant agent (Goose, Codex, Gemini CLI, Cline, Copilot, etc.)
as a subprocess inside a Docker container and communicates via the
standard ACP protocol (JSON-RPC over stdio).

**Bridge runtime** (`src/worker/acp_bridge.rs`):
- Spawns agent subprocess, performs ACP handshake (initialize → session → prompt)
- Translates ACP SessionNotification events to IronClaw's JobEventPayload stream
- Auto-approves permissions (Docker container is the security boundary)
- Supports follow-up prompts from the orchestrator
- Detects agent process exit via oneshot channel to prevent infinite polling

**User configuration** (mirrors MCP server pattern):
- `ironclaw acp add/list/remove/toggle/test` CLI commands
- DB-backed persistence with `~/.ironclaw/acp-agents.json` disk fallback
- Per-agent `enabled` flag + global `ACP_ENABLED` toggle
- `ironclaw acp test` spawns agent, verifies ACP handshake, reports capabilities

**System integration**:
- `ExtensionKind::AcpAgent` in extension manager (12 match arms)
- `agent_name` parameter in CreateJobTool resolves agent from AcpAgentsFile
- Mode stored as `"acp:<agent_name>"` for restart support
- Doctor validation, status display, boot screen, app startup logging
- Web UI: extension install mapping, job restart, follow-up prompt support

Closes #1506

* test: add comprehensive ACP test coverage (22 new tests)

Bridge: ToolCall, ToolCallUpdate, thought-image, max_turn_requests,
session_id propagation, text_from_content_block, multibyte truncation.

Config: AcpModeConfig defaults, settings resolution, env overrides.

Job tool: schema includes "acp" mode + agent_name, mode="acp" requires
agent_name parameter, JobMode::Acp as_str/display.

Job manager: JobMode::Acp as_str/display, acp_memory_limit_mb default.

CLI: parse_env_var valid/invalid/equals-in-value, command variants.

* refactor: make IronClawAcpClient reusable for CLI test command

Extract AcpEventSink trait so the same Client implementation (permission
auto-approval, event translation) is shared between the container bridge
(posts to orchestrator HTTP API) and the CLI test command (prints to stdout).

Also extracts ironclaw_init_request() to avoid duplicating the ACP
handshake parameters between bridge and test command.

* fix(sandbox): use host.docker.internal on all platforms for orchestrator URL

The orchestrator host was hardcoded to 172.17.0.1 on Linux, which is
only correct for the default Docker bridge network. Environments with
custom bridge IPs break container-to-host connectivity.

Since all containers already set extra_hosts with host-gateway, using
host.docker.internal works on all platforms and network configurations.

* fix ACP PR review feedback

* fix ACP DB error fallback

* fix clippy after staging merge

---------

Co-authored-by: Rajul Bhatnagar <brajul@amazon.com>
Co-authored-by: Firat Sertgoz <f@nuff.tech>

.env.example

@@ -208,6 +208,12 @@ HEARTBEAT_NOTIFY_USER=default
 # SANDBOX_TIMEOUT_SECS=120
 # SANDBOX_MEMORY_LIMIT_MB=2048
 
+# ACP (Agent Client Protocol) agents
+# ACP_ENABLED=false                       # Enable ACP agent sandbox mode
+# ACP_MEMORY_LIMIT_MB=4096               # Memory limit for ACP containers
+# ACP_TIMEOUT_SECS=1800                  # Maximum session timeout
+# Configure agents via CLI: ironclaw acp add goose --command goose --arg "--stdio"
+
 # Safety settings
 SAFETY_MAX_OUTPUT_LENGTH=100000
 SAFETY_INJECTION_CHECK_ENABLED=true