ci(chapel): unblock Compile Chapel Metalayer + Build & Test Zig FFI Bridge

Chapel-CI has been red on every push since the workflow + sources
were authored (commit e44815a, 2026-04-20) — zero successful runs in
the 100-run history. Two independent pre-existing breakages:

## Job 1: `Compile Chapel Metalayer` — `extern "C" { ... }` parse error

`chapel_ffi_exports.chpl` wrapped its 35 prover-id / category-id
`c_int` constants in a single `extern "C" { ... }` block. That syntax
is the Chapel "extern blocks" feature, which requires the Chapel
compiler to be built with LLVM + clang headers available. The
official `chapel-2.3.0-1.ubuntu24.amd64.deb` the workflow installs is
not built with that combination — so the parser bails at line 29:

  chapel_ffi_exports.chpl:29: syntax error: near '{'
  …
  parallel_proof_search.chpl:186: syntax error: near 'proc'   (cascade)

The constants are also `#define`d on the C side in
`src/zig_ffi/chapel_ffi_exports.h` — that is the canonical copy any
non-Chapel consumer reads. The Chapel copy only needs to be visible
to Chapel code; emitting it as a C-visible symbol via an `extern`
block is unnecessary. Dropping the wrapper and keeping the 35
declarations as plain module-level `const`s fixes the parse without
losing any contract. (Documented in-place; the comment block above
the constants points to the C header as the source of truth.)

## Job 2: `Build & Test Zig FFI Bridge` — Zig 0.14 API on 0.13 install

`src/zig_ffi/build.zig` line 1 already documents
`// Compatible with Zig 0.14+/0.15+`. Lines 23, 52, 74 use
`b.addLibrary(.{ ... .linkage = … })` which is the 0.14+ unified
`Build.addLibrary` API; Zig 0.13 only exposes the older
`addSharedLibrary` / `addStaticLibrary`. The workflow pinned
`mlugg/setup-zig@… with: version: 0.13.0` for both `zig-ffi` and
`rust-chapel-real` jobs, so every run hit:

  build.zig:23:18: error: no field or member function named 'addLibrary' in 'Build'

Bumping both pins to `0.14.0` matches what the source already
declares.

## Effect

Both jobs should compile on this branch. `rust-chapel-feature` (Job
3) was previously skipped via the `needs: zig-ffi` dependency — with
Job 2 green, Job 3 actually runs. Job 4 (`rust-chapel-real`) is
`continue-on-error: true` so its outcome stays advisory.

Surfaced during the 2026-05-30 dependabot-deadlock triage as one of
the orthogonal failures on PR #128. None of these jobs are required
checks, so this PR doesn't unblock anything blocking the merge queue
— it just makes Chapel L2.1 actually verifiable on CI for the first
time, which matters as L2.2-L2.7 land.

Refs: handover/TODO.md P3 "L2.1 ✅ Done" — the "done" status was
based on local builds; CI verification has been broken from day 1.

Author: hyperpolymath

.github/workflows/chapel-ci.yml

@@ -75,7 +75,7 @@ jobs:
       - name: Install Zig
         uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
         with:
-          version: 0.13.0
+          version: 0.14.0
 
       - name: Build Zig FFI library (with Chapel stubs)
         run: cd src/zig_ffi && zig build -Doptimize=ReleaseSafe
@@ -140,7 +140,7 @@ jobs:
       - name: Install Zig
         uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
         with:
-          version: 0.13.0
+          version: 0.14.0
 
       - name: Install Rust
         uses: dtolnay/rust-toolchain@4be9e76fd7c4901c61fb841f559994984270fce7 # stable