[alpha.5] T4.2 Merge alias/workspace/subpath resolvers into one module

[SisyphusZheng]

Parent\n\n#132\n\n## What to build\n\nCombine alias-utils.ts, workspace-alias.ts, subpath-resolver.ts, and ssg-package-resolver.ts into a single tested resolver module that handles local source aliases, npm/jsr export maps, subpath exports, and remote packages.\n\n## Acceptance criteria\n\n- [ ] One resolver module replaces the four existing modules.\n- [ ] Local source aliases expand known OpenElement subpaths before root aliases swallow them.\n- [ ] No regression in Vite dev/build resolution.\n- [ ] Old modules deleted and imports updated.\n\n## Blocked by\n\n- #162

[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Closing as completed or superseded by the alpha.5 train.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SPA mode + client router + desktop proof) was merged and its Alpha.5 Issue Coverage table marks the alpha.5 items done/superseded and lists them for closure: feat(alpha.5): SPA mode + client router + desktop proof #121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.