feat(fleet): add MCP channel server for real-time agent communication

[Wirasm]

Summary

Adds a kild-fleet MCP channel server that watches inbox files and pushes notifications into Claude Code sessions via the channels protocol. Reduces fleet communication latency from ~1s (Claude inbox polling) to ~100ms (fs.watch + stdio notification). Also exposes MCP tools so agents can write status/reports/messages without shelling out to CLI commands.

Changes

• New: integrations/channel.rs — installs channel server, patches .mcp.json, cleanup on destroy
• New: kild init-channels CLI command — installs server.ts + bun deps at ~/.kild/channels/fleet/
• New: FleetConfig in kild-config with [fleet] channels toggle (default: false)
• Modified: fleet_agent_flags() appends --dangerously-load-development-channels server:kild-fleet when channels enabled
• Modified: daemon_spawn.rs calls setup_channel_integration() in the spawn sequence
• Modified: destroy.rs cleans up .mcp.json from project root for --main sessions

Architecture

Agent brain (Claude session)         Agent worker (Claude session)
  └─ kild-fleet MCP server            └─ kild-fleet MCP server
       │  fs.watch(KILD_FLEET_DIR)         │  fs.watch(KILD_INBOX)
       │                                   │
       └──── ~/.kild/inbox/<project>/ ─────┘
              (existing file protocol)

The channel server is a TypeScript/Bun MCP server embedded as a string constant in the Rust binary. It reads $KILD_INBOX and $KILD_FLEET_DIR from the PTY environment (already injected by the inbox module). The file-based inbox protocol remains the source of truth — the channel is a notification + tooling layer on top.

MCP Tools Exposed

Tool	Role	Action
report_status	worker	Write status + optional report.md
send_to_brain	worker	Write task.md to brain's inbox
send_to_worker	brain	Write task.md to worker's inbox
list_fleet	both	List fleet members with status

Files Changed

15 files changed (+616, -23)

File list

• crates/kild-core/src/sessions/integrations/channel.rs (new, 442 lines)
• crates/kild/src/commands/init_channels.rs (new, 59 lines)
• crates/kild-config/src/types.rs — FleetConfig struct
• crates/kild-config/src/loading.rs — merge logic
• crates/kild-config/src/lib.rs — re-export
• crates/kild-core/src/lib.rs — re-export
• crates/kild-core/src/sessions/daemon_spawn.rs — wire channel integration
• crates/kild-core/src/sessions/fleet.rs — channels flag in fleet_agent_flags()
• crates/kild-core/src/sessions/destroy.rs — .mcp.json cleanup
• crates/kild-core/src/sessions/daemon_helpers.rs — re-export
• crates/kild-core/src/sessions/integrations/mod.rs — register module
• crates/kild-paths/src/lib.rs — channels_dir(), fleet_channel_dir()
• crates/kild/src/app/misc.rs — init-channels clap def
• crates/kild/src/app/mod.rs — subcommand registration
• crates/kild/src/commands/mod.rs — dispatch

Testing

• cargo fmt --check && cargo clippy --all -- -D warnings passes
• cargo test --all passes (0 failures)
• cargo build --all succeeds
• E2E: kild init-channels installs server + deps
• E2E: Brain create gets .mcp.json + channels flag
• E2E: Worker create gets .mcp.json + channels flag
• E2E: kild inject → worker receives task, writes status + report
• E2E: Brain destroy cleans up .mcp.json from project root
• E2E: Graceful degradation when [fleet] channels = false (no .mcp.json, no flag)

Configuration

[fleet]
channels = true  # default: false (research preview)

Requires Bun runtime. Run kild init-channels to install dependencies.