chore: commit remaining pre-existing changes

- Agent configs (.opencode/agents/)
- Backend: alembic, routes, app, utils, scripts
- Frontend: package.json, vite, components, e2e infra
- Specs: 028-llm-datasource-supeset updates
- Docker e2e config and Playwright setup

.opencode/agents/reflection-agent.md

@@ -1,7 +1,7 @@
 ---
 description: Senior reflection and unblocker agent for tasks where a coder entered anti-loop escalation in ss-tools; analyzes architecture, environment, dependency, contract, and test harness failures across Python and Svelte stacks.
 mode: subagent
-model: opencode/big-pickle
+model: opencode-go/deepseek-v4-flash
 temperature: 0.0
 permission:
   edit: allow