fix(0115): source-aware global selection — own-wins for module globals

The globals registry (global_names) was last-wins across modules with no
per-importer gate: any module's bare K could read/write/type against an
unrelated module's same-named global (hash.sx's K table hijacked every
user K once std's namespace tail pulled hash into the program), and an
own const of an unsupported shape borrowed another module's const and
panicked at the unresolved-type tripwire.

- var_decl joins RawDeclRef: module globals are selectable raw authors.
- selectGlobalAuthor (the globals analogue of F2's selectModuleConst):
  own author wins, one flat-visible author resolves, >=2 distinct flat
  authors diagnose loudly, authored-but-not-visible diagnoses, and a
  compiler-synthesized global (no raw author) emits untracked. A var_decl
  author whose per-source registration was deduped at flat-merge (two
  modules declaring the same extern symbol) serves the symbol's
  registration.
- All bare-identifier global sites route through it: value read, addr-of,
  assignment (store + compound), lvalue address, fn-ptr call, call param
  typing, and expression type inference.
- selectModuleConst gains .own_opaque: an own const author with no
  materialized per-source value (e.g. an array '::' const) blocks
  borrowing another module's same-named const — the read diagnoses
  cleanly instead of panicking.
- The fn-as-VALUE arm admits raw-facts-only authors: an own fn whose name
  a flat-merge collision dropped from the global decl list (first-wins)
  now resolves via author selection for func_ref/closure/Any shapes too.

Regressions: examples 0835 (own const vs flat array global), 0836 (main
const vs namespaced array global, incl. inference), 0837 (own array
const never borrows cross-module — clean unresolved).

issues/0115-same-name-const-scalar-array-collision.md

@@ -1,5 +1,23 @@
 # 0115 — same-name consts of different shapes collide across modules (panic / silent clobber)
 
+> **RESOLVED** (2026-06-11). Root cause: the globals registry
+> (`global_names`) is last-wins across modules and every read/write/addr/
+> call site consulted it with no source-awareness; `var_decl` was not even
+> a selectable raw author. Fix: `var_decl` joins `RawDeclRef`;
+> `selectGlobalAuthor` (the globals analogue of F2's `selectModuleConst`)
+> selects the author own-wins / one-flat-visible / ambiguous-loudly and
+> serves the AUTHOR's per-source global; all bare-identifier global sites
+> (read, addr-of, assignment, fn-ptr call, type inference) route through
+> it. `selectModuleConst` gained `.own_opaque` so an own const author with
+> no materialized value (unsupported shape, e.g. an array `::` const)
+> blocks borrowing another module's same-named const instead of panicking.
+> The fn-as-VALUE arm admits raw-facts-only authors (an own fn dropped from
+> the global decl list by a flat-merge collision — the 0601 `test` case).
+> Regression tests: examples/0835, 0836, 0837. The co-blockers also
+> landed: dead-global elimination at emit (unreferenced plain-data globals
+> are not emitted) and 1055/1056 no longer pin global error ordinals —
+> the full std namespace tail is enabled on top.
+
 **Symptom.** When two modules in one program declare a same-named module
 const with DIFFERENT shapes (scalar `K : s64 : 4` vs array
 `K : [4]s64 : .[...]`), resolution conflates them instead of selecting