feat: allow quantity-keyed coordinate map literals

[shunsuke-shimomura]

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Summary

• accept quantity expressions as keys in map and table literals for coordinate indexes
• defer contextual map-axis selection to TIR expected-type inference, including nested map literals
• store checked map axes as TIR facts consumed by evaluation and presentation
• validate dimensions, static evaluability, grid membership, coverage, duplicates, and coordinate display metadata
• update formatter, LSP traversal, grammar, documentation, and regression coverage

This addresses graphcal-lang/graphcal#1370.

AI assistance

• AI used: yes — Codex assisted with implementation, tests, and validation
• Human review of AI-assisted code: partial

Breaking changes

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

Validation

• cargo clippy --workspace --all-targets -- -D warnings
• cargo test -p graphcal-eval --test edge_case_bugs
• prek run --all-files
• cargo fmt --all -- --check
• git diff --check

The workspace test run passed the compiler, evaluator, formatter, LSP, and all 160 CLI tests. One unrelated Unix-socket plugin test could not run in the sandbox because socket creation returned Operation not permitted.