fix(lower): fn-value site lazily lowers winner only on resolver .none [0102d F1]

The bare-fn-as-value site (func_ref / fn-ptr / closure coercion) eagerly
lazily-lowered the name-keyed first-wins WINNER before the resolveBareCallee
block could reroute a genuine flat same-name collision to its per-source
author. Taking a SHADOW author's fn value therefore lowered (and could
mis-diagnose) the unused winner's body. Move lazyLowerFunction INSIDE blk_fv
onto the `.none` fallback only, mirroring the closure(fn) and free-function
UFCS sites: on `.func` use the resolved author's FuncId and never touch the
winner; on `.none` fall through to lazy-lower + resolveFuncByName the winner.

Regression: examples/0735-modules-flat-same-name-fn-value-winner — the
first-wins winner's body is independently broken and never used; a shadow
taken as a function value binds the shadow and runs (exit 0) while the winner
is not lowered. Fails-before (unresolved symbol in the winner), passes-after.

examples/0735-modules-flat-same-name-fn-value-winner.sx

@@ -0,0 +1,17 @@
+// fix-0102d site 2 / attempt-2 (issue 0102): the first-wins winner's body is
+// independently BROKEN (references an undefined symbol) and is never used. A
+// shadow author from a later flat import takes its OWN `pick` as a function
+// VALUE (`g : () -> s64 = pick`). The value must bind the shadow (own-author
+// wins) and the broken winner must NOT be lowered — a rerouted fn value never
+// uses the winner. Before the fix the fn-value site eagerly lazily-lowered the
+// name-keyed winner BEFORE the resolver rerouted, surfacing the winner's
+// `unresolved 'missing_from_a'` for a function the value never touches.
+// Regression: per-source function-value conversion must not pre-lower the winner.
+#import "modules/std.sx";
+#import "0735-modules-flat-same-name-fn-value-winner/a.sx";
+#import "0735-modules-flat-same-name-fn-value-winner/b.sx";
+
+main :: () -> s32 {
+    print("from_b_value = {}\n", from_b_value());
+    0
+}

examples/0735-modules-flat-same-name-fn-value-winner/a.sx

@@ -0,0 +1,4 @@
+// a.sx authors `pick` (imported first → the first-wins name-keyed winner) but
+// its body references an undefined symbol, so lowering a.pick AT ALL is an
+// error. Nothing uses a.pick — taking b.pick as a value must not pre-lower it.
+pick :: () -> s64 { return missing_from_a(); }

examples/0735-modules-flat-same-name-fn-value-winner/b.sx

@@ -0,0 +1,7 @@
+// b.sx authors its OWN `pick` (returns 2) and takes it as a function VALUE. The
+// value binds b.pick (own-author wins), never the broken winner from a.sx.
+pick :: () -> s64 { return 2; }
+from_b_value :: () -> s64 {
+    g : () -> s64 = pick;
+    return g();
+}

examples/expected/0735-modules-flat-same-name-fn-value-winner.exit

@@ -0,0 +1 @@
+0

examples/expected/0735-modules-flat-same-name-fn-value-winner.stderr

@@ -0,0 +1 @@
+

examples/expected/0735-modules-flat-same-name-fn-value-winner.stdout

@@ -0,0 +1 @@
+from_b_value = 2

issues/0102-flat-import-same-signature-collision.md

@@ -60,7 +60,9 @@ collision:
      args fill from the RESOLVED author's defaults, not the winner's.
   2. **Function-value conversion** (`closure(fn)` and the bare-fn-as-value
      `func_ref` / fn-ptr / closure-coercion path): captures the resolved
-     author's FuncId.
+     author's FuncId. The winner's body is lazily lowered ONLY on the `.none`
+     fallback — a rerouted value never uses the winner, so taking a shadow as a
+     value must not pre-lower (and possibly mis-diagnose) the winner's body.
   3. **Free-function UFCS** (`recv.fn()` → `fn(recv, …)`): dispatches the
      resolved author for the receiver's source.
   4. **Comptime `#run`** of a bare call: `lowerMainAndComptime` now sets
@@ -71,7 +73,7 @@ collision:
 
 ## Regression tests
 
-`examples/0722`–`0734` (each a focused multi-file flat-collision scene that
+`examples/0722`–`0735` (each a focused multi-file flat-collision scene that
 fails on pre-fix code and passes after):
 
 - `0722-modules-flat-same-name-own` — own-author wins on the call path.
@@ -93,3 +95,8 @@ fails on pre-fix code and passes after):
   callee.
 - `0734-modules-flat-same-name-ufcs-ambiguous` — `≥2` flat authors, UFCS call
   → loud diagnostic (pre-fix: silently bound the winner).
+- `0735-modules-flat-same-name-fn-value-winner` — the first-wins winner's body
+  is independently broken and never used; a shadow taken as a function value
+  binds the shadow and runs while the winner is NOT lowered (pre-fix: the
+  fn-value site eagerly lowered the winner before the resolver rerouted,
+  surfacing the winner's error for a function the value never touches).

src/ir/lower.zig

@@ -3250,14 +3250,13 @@ pub const Lowering = struct {
                         const str = self.builder.constString(sid);
                         break :blk self.builder.boxAny(str, .string);
                     }
-                    if (!self.lowered_functions.contains(eff_fn_name)) {
-                        self.lazyLowerFunction(eff_fn_name);
-                    }
                     // fix-0102d site 2: taking a bare same-name fn as a VALUE
                     // (func_ref, fn-ptr / closure coercion) must capture the
                     // RESOLVED author's FuncId for a genuine flat collision, not
                     // the first-wins winner's. Plain bare name only; `.ambiguous`
-                    // → loud diagnostic; `.none` → existing first-wins path.
+                    // → loud diagnostic; `.none` → existing first-wins path. The
+                    // winner is lazily lowered ONLY on `.none` — a rerouted value
+                    // never uses the winner, so its body must not be lowered.
                     const value_fid: ?FuncId = blk_fv: {
                         if (std.mem.eql(u8, eff_fn_name, id.name) and
                             self.program_index.ufcs_alias_map.get(id.name) == null and
@@ -3275,6 +3274,9 @@ pub const Lowering = struct {
                                 }
                             }
                         }
+                        if (!self.lowered_functions.contains(eff_fn_name)) {
+                            self.lazyLowerFunction(eff_fn_name);
+                        }
                         break :blk_fv self.resolveFuncByName(eff_fn_name);
                     };
                     if (value_fid) |fid| {