test: cover graph-ref alias boundaries with and without overlay bindings

[shunichironomura]

Warning

This content was written by an AI agent and must be verified by a human developer. After human verification, this alert may be removed.

Summary

• Adds an HIR expression-lowering test with four cases: @imported::name may read only instance-independent consts, and @included::name may read graph values. Each rule is checked twice: when the module resolver reaches the path, and when an overlay binding the resolver cannot see supplies it.
• This is the test from refactor: preserve resolver source-path boundaries #2037, kept on its own. The resolver refactor in that PR was dropped as not worth doing; see the closing comment on Classify alias.member once during HIR lowering #1952. Test-only change: no compiler, diagnostic or editor behavior changes.

Validation

• cargo fmt --all --check, cargo clippy -p graphcal-compiler --tests -- -D warnings, and cargo test -p graphcal-compiler --lib hir::expr_lower (30 passed) all pass.

AI assistance

• AI used: yes — the test was written by an agent in refactor: preserve resolver source-path boundaries #2037; an agent extracted it and prepared this PR.
• Human review of AI-assisted code: pending.

Breaking changes

• No breaking changes
• Breaking changes; the breaking change label is applied

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https://claude.ai/code/session_01B2t1wANbEx5VhUyvdThmbW

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