[alpha.5] T3.3 Refactor openElement() / openPipeline() as pure wiring

[SisyphusZheng]

Parent\n\n#131\n\n## What to build\n\nReduce @openelement/adapter-vite entry points to configuration normalization + plugin composition. The framework behavior must be delegated to @openelement/ssg.build().\n\n## Acceptance criteria\n\n- [ ] index.ts / app-vite.ts read as wiring, not policy.\n- [ ] Line count in adapter-vite drops significantly.\n- [ ] Public API signatures unchanged.\n- [ ] All build paths still pass.\n\n## Blocked by\n\n- #170

[SisyphusZheng]

Closing as completed or superseded by the alpha.5 train.

Evidence:

• PR feat(alpha.5): SPA mode + client router + desktop proof #121 (feat(alpha.5): SPA mode + client router + desktop proof) was merged and its Alpha.5 Issue Coverage table marks the alpha.5 items done/superseded and lists them for closure: feat(alpha.5): SPA mode + client router + desktop proof #121
• v0.41.0-alpha.5 was published as a GitHub prerelease: https://github.com/open-element/openelement/releases/tag/v0.41.0-alpha.5
• The AutoFlow release workflow for v0.41.0-alpha.5 completed successfully: https://github.com/open-element/openelement/actions/runs/28499891702

The post-release package condition for #120 is now satisfied by the published 0.41.0-alpha.5 package line.