fix(ir): exhaustive named-const array dims (0083) + nested slice-literal coercion (0085)

Makes the F0.4 fixes exhaustive across every resolution / nesting path.

0083 — named-const array dimension, stateless paths. Attempt 1 fixed the
stateful resolver (direct local decls, struct fields, params, returns) but the
binding-free registration-time resolver (`type_bridge`, used for type aliases
`Arr :: [N]T` and inline union/enum field types) still resolved a named dim with
a silent `else 0`, so `Arr :: [N]s64; a : Arr` and `union { a: [N]s64 }` were
still miscompiled (garbage / bus error). Thread the module-global const table
(`ProgramIndex.module_const_map`) into `type_bridge` alongside the alias map, so
`StatelessInner.resolveArrayLen` resolves a named module-const dim to the same
length everywhere. The remaining unresolvable case (a computed/comptime dim on
the binding-free path, which the stateful path hard-errors) now bails LOUDLY
instead of fabricating a 0 length.

0085 — nested slice-literal elements. `lowerArrayLiteral` lowered each element
with the element type as target but appended the raw value. A nested `.[...]`
element at a slice element type (`[][]s64`) still lowers to an aggregate array
`[N]T`, so the outer aggregate held raw arrays where slice {ptr,len} headers
were expected — indexing the inner slice read a garbage pointer and segfaulted.
After lowering each element, coerce a same-element array to the slice element
type via the existing `array_to_slice` op. The coercion recurses with the
nesting, so `[][]T` and deeper materialize at every level — local-bound AND
direct-call-argument forms.

Regressions (fail-before/pass-after demonstrated on the pre-fix compiler):
  examples/0140-types-named-const-array-dim.sx — extended with type-alias,
    nested [N][M]T, and union-field named dims (s64 / string / struct elems)
  examples/0142-types-nested-slice-literal-elements.sx — [][]s64 + [][]string,
    local-bound vs direct-arg
  src/ir/type_bridge.test.zig — named-const dim resolves to literal length

Gate: zig build, zig build test, bash tests/run_examples.sh (388 passed).
Issues 0083 and 0085 marked RESOLVED.

examples/expected/0140-types-named-const-array-dim.stdout

@@ -1,3 +1,7 @@
 scalar a0=7 a3=42
 string s0=hi s1=yo
 struct p0x=1 p0y=2 p2x=5
+alias a0=11 a3=99
+alias s0=al s2=ok
+nested g00=1 g32=8
+union u0=70 u3=7

examples/expected/0142-types-nested-slice-literal-elements.exit

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

examples/expected/0142-types-nested-slice-literal-elements.stderr

@@ -0,0 +1 @@
+

examples/expected/0142-types-nested-slice-literal-elements.stdout

@@ -0,0 +1,4 @@
+num local=10
+num direct=10
+str local=4
+str direct=4