[alpha.5] T4.1 Define resolver contract in protocol

[SisyphusZheng]

Parent

#132

What to build

Define a single resolver contract in @openelement/protocol for local source aliases, npm/jsr package exports, subpath exports, and remote package resolution.

Acceptance criteria

• Resolver input/output types live in protocol.
• Error types for unresolvable subpaths / bad export maps are defined.
• Contract is imported by the unified resolver implementation in @openelement/adapter-vite / @openelement/ssg.

Blocked by

• [alpha.5] T1 - Define package contracts and public/internal surfaces #129

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Closing as completed or superseded by the alpha.5 train.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SPA mode + client router + desktop proof) was merged and its Alpha.5 Issue Coverage table marks the alpha.5 items done/superseded and lists them for closure: feat(alpha.5): SPA mode + client router + desktop proof #121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