Propagate module dialect before compilation

[aqk]

Summary

• Apply the detected module dialect before frontend, cache lookup, and module compilation.
• Enable module-only CSE dominance semantics even when callers enter module compilation with default options.

Test plan

• cargo test test_unlabeled_module_file
• cargo test test_cse_tricky_2

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Note

Medium Risk
Touches core compile entry and optimizer dialect flags; wrong detection or dialect propagation could change codegen or cache behavior for module inputs.

Overview
compile_pre_forms now runs detect_chialisp_module on raw pre-forms and updates opts with the module dialect and stdenv (from dialect.strict) before frontend, so module files get the right language settings even when compilation starts with default options (affects parsing, disk cache keys, and the module path).

In compile_module, cse_dominance is always turned on for modules instead of only when stepping < 26, so module CSE dominance semantics apply consistently regardless of stepping on the incoming dialect.

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