feat(FN-008): replace RunFusion with OpenCode manifest

- Remove runfusion.yml, add opencode.yml with web terminal config
- Update all references across codebase (tests, docs, specs)
- Add OpenCode container setup with port 3000 and health checks

apps/api/app/tools/manifests/opencode.yml

@@ -0,0 +1,42 @@
+id: opencode
+name: OpenCode
+description: AI-powered terminal-based development environment with web interface.
+version: "1.0.0"
+image: ghcr.io/opencode-ai/opencode:latest
+runtime_working_dir: /workspace
+ports:
+  - container_port: 3000
+    protocol: tcp
+    name: http
+    primary: true
+workspace_mounts:
+  - type: volume
+    source_pattern: "{project_repo}"
+    target: /workspace
+    read_only: false
+config_mounts:
+  - type: volume
+    source_pattern: "{user_config}/opencode"
+    target: /root/.config/opencode
+    read_only: false
+env:
+  TERM: xterm-256color
+  FORCE_COLOR: "1"
+health_check:
+  type: http
+  path: /
+  port: 3000
+  interval_seconds: 10
+  timeout_seconds: 5
+  retries: 3
+  start_period_seconds: 15
+resource_limits:
+  cpus: 2.0
+  memory_mb: 4096
+  memory_swap_mb: -1
+traefik:
+  enabled: true
+  subdomain_prefix: opencode
+  port: 3000
+  middlewares: []
+  strip_prefix: false