[codex] resolve dynamic import literal-union params

[andrewtdiz]

Part of #1674.

Scope

• Preserve inline TypeScript string literal type values in HIR as StringLiteral while keeping runtime/codegen treatment equivalent to String.
• Collect function and closure parameters annotated with finite all-string-literal union types.
• Feed those parameter candidate sets into dynamic import() and new Worker() path resolution alongside existing const/local resolution.
• Add Node parity coverage for direct import(specifier) and template interpolation over a literal-union parameter.

Non-goals

• Type alias expansion beyond what existing lowering already provides.
• Mixed or broad string unions such as "./a.ts" | string.
• Later assignment/reaching-definition analysis.
• Package/bare wildcard imports or unbounded glob discovery.

Validation

• npm exec --yes --package=node@26 -- node --experimental-strip-types test-parity/node-suite/module/loader/dynamic-import-param-union.ts
• CARGO_TARGET_DIR=/tmp/perry-param-union-check cargo check -p perry-hir -p perry-codegen -p perry -p perry-runtime
• CARGO_TARGET_DIR=/tmp/perry-param-union-check cargo test -p perry-hir dynamic_import -- --nocapture
• CARGO_BUILD_JOBS=1 CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-param-union-build cargo build --release -p perry -p perry-runtime -p perry-stdlib
• Direct Perry compile/run of test-parity/node-suite/module/loader/dynamic-import-param-union.ts
• PERRY_NO_AUTO_OPTIMIZE=1 CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-param-union-build npm exec --yes --package=node@26 -- bash -lc './run_parity_tests.sh --suite node-suite --module module --filter dynamic-import-param-union'
• PERRY_NO_AUTO_OPTIMIZE=1 CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-param-union-build npm exec --yes --package=node@26 -- bash -lc './run_parity_tests.sh --suite node-suite --module module --filter dynamic-import'
• cargo fmt --all -- --check
• git diff --check
• ./scripts/check_file_size.sh