Fleet Panel: remote host settings (DB path, port, binary, logs) #355

Acceptance Criteria

• Host Settings section visible in the Fleet Panel when in fleet mode (server or client)
• Settings exposed:
  • Session database path (where the opencode server stores sessions)
  • Server port (what port the canonical server listens on)
  • Binary path (which opencode binary the server runs)
  • Log directory (where server logs are written)
• Read settings: on panel load and on explicit refresh, reads current values from the
  canonical server machine (over SSH for clients; locally for servers)
• Write settings: inline edit → save → writes the config on the host machine
• Restart required indicator: after a setting change that requires restart, shows a
  yellow "Restart required" badge with a "Restart Server" button
• One-click restart: stops + starts the launchd/systemd service on the canonical
  server (over SSH for clients; locally for servers)
• Validation: port must be numeric 1024-65535; paths must be absolute; binary path
  must exist on the host (validated before save)
• Hidden when standalone: section not rendered when fleet role is standalone

Testing Decisions

• Unit test: fleet_host_settings.test.ts — mock SSH reads/writes, verify correct
  commands generated for each setting
• Unit test: validation logic — invalid port, relative path, missing binary → rejected
  with specific error
• Unit test: restart-required detection — which settings trigger it (port, binary, DB path)
  vs. which don't (log dir)

Key Decisions

Constraints & Invariants

• Settings MUST NOT be cached stale — always read from the host on panel open/refresh
• Write is atomic (tmp + mv) on the host side
• Restart waits for health probe confirmation (server back up) before clearing the indicator

Source

Part of #350
Blocked by #354
ADR 0007: docs/adr/0007-fleet-panel-and-profile-ui.md