refactor(hir): cut over to the symbol/scope core

[hongjr03]

Summary

First slice of #288, split out for independent review. Introduces the open symbol/scope foundation that the rest of the SystemVerilog semantic work builds on.

• Cut over scopes to DefId/DefLoc/DefKind (replaces ModuleDefOrigin).
• Activate PerNs type/value lookup, package import/export resolution, and package export signature narrowing.
• Refactor subroutines to InContainer<LocalSubroutineId> container handles (drops the globally-interned SubroutineId).
• Unify the per-scope structs into a single NameScope.

Validation

• `cargo fmt --all -- --check`
• `cargo clippy --workspace --all-targets -- -D warnings`
• `cargo test --workspace` (477 passed)

Notes

Class/interface specialization, assertions, package/class :: constructs, hierarchical path resolution, and the type ADT expansion land in the stacked follow-up PRs.