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/runfusion-manifest/spec.md

@@ -0,0 +1,15 @@
+## ADDED Requirements
+
+### Requirement: OpenCode manifest defines web terminal environment
+The system SHALL provide an OpenCode manifest with web terminal configuration.
+
+#### Scenario: Manifest includes terminal config
+- **WHEN** the OpenCode manifest is loaded
+- **THEN** it specifies an OpenCode Docker image with web interface
+- **AND** it defines exposed ports for the HTTP interface (port 3000)
+- **AND** it defines volume mounts (workspace, config)
+
+#### Scenario: Manifest includes health check
+- **WHEN** the manifest is used for spawning
+- **THEN** it defines a health check endpoint
+- **AND** specifies health check interval and timeout