docs(openspec): add OpenSpec changes for FN-005, FN-006, FN-008, FN-009, FN-010

- Add frontend-foundation change (FN-005) with 46 tasks
- Add deployment-config change (FN-006) with 27 tasks
- Add runfusion-poc/opencode-poc change (FN-008) with 25 tasks
- Add config-secrets change (FN-009) with 31 tasks
- Add codeserver-spawn change (FN-010) with 38 tasks
- Include project specsheet and configuration
- Archive completed deployment-config change

openspec/changes/runfusion-poc/specs/executable-environment/spec.md

@@ -0,0 +1,27 @@
+## ADDED Requirements
+
+### Requirement: Container provides web terminal interface
+The system SHALL provide a web terminal interface in the OpenCode container.
+
+#### Scenario: Terminal available
+- **WHEN** the OpenCode container is running
+- **THEN** a web terminal is accessible via HTTP on port 3000
+- **AND** the user can execute shell commands through the browser
+
+#### Scenario: Workspace access
+- **WHEN** the container runs
+- **THEN** the project workspace is mounted at /workspace
+- **AND** the user can read/write files in the workspace
+
+### Requirement: Container supports AI features
+The system SHALL allow AI-powered development features in the OpenCode environment.
+
+#### Scenario: AI assistance
+- **WHEN** the user interacts with OpenCode
+- **THEN** AI features are available for code completion and assistance
+- **AND** the user can configure AI provider settings
+
+#### Scenario: Terminal session persistence
+- **WHEN** the user opens a terminal session
+- **THEN** the session persists while the container runs
+- **AND** multiple sessions can be opened