Fix release mind map generation

[wangsoft]

Summary

• package the agent worker, Node runtime, and OpenCode runtime inside release builds instead of invoking the source-tree build on end-user machines
• stage and verify the worker resources across release workflows while preserving the existing debug-mode build behavior
• extract EPUB reading-order text for mind-map requests so legacy imported books no longer send only the [EPUB 书籍] placeholder
• add focused coverage for packaged runtime layouts, stale bundles, EPUB extraction, invalid archives, and release workflow ordering

Testing

• npm run test:bundle — 30 Vitest tests and 2 staging tests passed
• cargo test --release --test agent_worker_test — 28 tests passed
• python3 -m unittest script/test_release_workflows.py -v — 4 tests passed
• npm run stage — worker, portable Node, and OpenCode runtimes staged successfully
• npm run tauri build -- --bundles app --config '{"bundle":{"externalBin":["binaries/openkoto-agent-node","binaries/opencode"],"resources":["resources/agent-worker"]}}' — macOS release app built successfully