Update Stage 3 plan for Stage 2 reality

Record program-level HIR/MIR, module namespaces, and per-module codegen/mangling.
Clarify core placement in sysroot and multi-module run-pass fixtures.

Author: sprajs

implementation_plans/STAGE3.md

@@ -46,6 +46,9 @@ Enable nominal user-defined types and enforce Wyrm’s ownership model end-to-en
 ## 1. Fixed inputs and prerequisites (do not reopen)
 
 - Stage 2 module system and static imports are in place.
+- HIR/MIR are program-level (`hir::Program`, `mir::Program`) with cross-module export tables; Stage 3 should extend these rather than reintroducing per-module-only flows.
+- Module-level `let` bindings are const-only and require explicit types (Stage 2 decision); Stage 3 should not assume runtime module init via top-level code.
+- Module namespaces and module-qualified path resolution are already implemented (imported modules bind namespaces; exports resolve via module paths).
 - Explicit `self` parameter in methods is required (WYRM §3.6).
 - Surface syntax does **not** expose `&` / `&mut` (ADR-0001).
 - Memory model uses ARC for shared ownership and deterministic drops.
@@ -67,6 +70,7 @@ Enable nominal user-defined types and enforce Wyrm’s ownership model end-to-en
 - `compiler/wyrmc_hir` / `wyrmc_typeck`: add type/impl/method tracking, ownership checks.
 - `compiler/wyrmc_mir`: add aggregate/field operations and drop/refcount statements.
 - `compiler/wyrmc_passes`: add ownership/drop elaboration pass.
+- `compiler/wyrmc_resolve`: already provides module graphs and resolution; Stage 3 should build on its output.
 - `libraries/wyrm_runtime`: add refcount and allocation helpers.
 - `libraries/wyrm_core`: add `Option`, `Result`, and ownership wrapper types.
 
@@ -212,6 +216,8 @@ borrows for views. Stage 3 must enforce:
 - [ ] Generate functions for struct/enum constructors and methods.
 - [ ] Lower drop glue calls into LLVM calls.
 - [ ] Lower refcount operations to runtime calls.
+- [ ] Use the existing Stage 2 mangling scheme for new symbols (`wyrm$<mod_path>$<name>`; keep `wyrm_main` unmangled).
+- [ ] Follow per-module LLVM emission (one LLVM module per Wyrm module).
 
 ---
 
@@ -225,6 +231,7 @@ borrows for views. Stage 3 must enforce:
 ### 10.2 Ownership wrappers
 - [ ] Provide surface wrappers for `Box[T]`, `Rc[T]`, `Arc[T]` in `core`.
 - [ ] Keep implementations minimal and compiler-friendly.
+- [ ] Place `core` modules under `<sysroot>/modules/core` to match Stage 2 sysroot resolution.
 
 ---
 
@@ -252,6 +259,7 @@ borrows for views. Stage 3 must enforce:
 - [ ] `Box` allocation + drop.
 - [ ] `Rc` clone/drop (refcount sanity).
 - [ ] `Option`/`Result` usage in `core`.
+- [ ] Use directory-based run-pass fixtures for multi-module tests (supported since Stage 2).
 
 ### 12.3 Compile-fail tests
 - [ ] Use-after-move.