Fix Fypp macro syntax and precheck coverage claims

- GPU macros use $: prefix (inline), not @: — matches all 400+ usages in src/
- GPU_PARALLEL, GPU_DATA, GPU_HOST_DATA are block macros using #:call/#:endcall
- Add block macro usage example
- Fix GPU_ROUTINE args: parallelism='[seq]', not function_name=
- Split forbidden patterns into precheck-enforced vs convention-enforced
  (goto, COMMON, save, stop are not checked by precheck.sh)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

.claude/rules/fortran-conventions.md

@@ -22,12 +22,15 @@ Every Fortran module follows this pattern:
 - Constants: descriptive names, not ALL_CAPS
 
 ## Forbidden Patterns
-These are caught by `./mfc.sh precheck` (source lint step 4/5):
+
+Caught by `./mfc.sh precheck` (source lint step 4/5):
 - `dsqrt`, `dexp`, `dlog`, `dble`, `dabs` → use `sqrt`, `exp`, `log`, `real(..., wp)`
 - `real(8)`, `real(4)` → use `wp` or `stp` kind parameters
+- Raw `!$acc` or `!$omp` directives → use Fypp GPU_* macros from `parallel_macros.fpp`
+
+Enforced by convention/code review (not automated):
 - `goto`, `COMMON` blocks, global `save` variables
 - `stop`, `error stop` → use `call s_mpi_abort()`
-- Raw `!$acc` or `!$omp` directives → use Fypp GPU_* macros from `parallel_macros.fpp`
 
 ## Precision Types
 - `wp` (working precision): used for computation. Double by default.

.claude/rules/gpu-and-mpi.md

@@ -22,21 +22,36 @@ compiles to either OpenACC or OpenMP target offload depending on the build flag:
 - `shared_parallel_macros.fpp` — Shared helpers (collapse, private, reduction generators)
 
 ### Key GPU Macros (always use the `GPU_*` prefix)
-- `@:GPU_PARALLEL_LOOP(collapse=N, private=[...], reduction=[...], reductionOp='+')` —
+
+Inline macros (use `$:` prefix):
+- `$:GPU_PARALLEL_LOOP(collapse=N, private=[...], reduction=[...], reductionOp='+')` —
   Parallel loop over GPU threads. Most common GPU macro.
-- `@:END_GPU_PARALLEL_LOOP()` — Required closing for GPU_PARALLEL_LOOP.
-- `@:GPU_PARALLEL(code, ...)` — GPU parallel region (wraps code block).
-- `@:GPU_LOOP(collapse=N, ...)` — Inner loop within a GPU parallel region.
-- `@:GPU_DATA(code, copy=..., create=..., ...)` — Scoped data region.
-- `@:GPU_ENTER_DATA(create=[...])` — Allocate device memory (unscoped).
-- `@:GPU_EXIT_DATA(delete=[...])` — Free device memory.
-- `@:GPU_UPDATE(host=[...])` — Copy device → host (before MPI send).
-- `@:GPU_UPDATE(device=[...])` — Copy host → device (after MPI receive).
-- `@:GPU_ROUTINE(function_name=..., nohost=True/False)` — Mark routine for device.
-- `@:GPU_DECLARE(copyin=[...], link=[...])` — Declare device-resident data.
-- `@:GPU_ATOMIC(atomic='update')` — Atomic operation on device.
-- `@:GPU_WAIT()` — Synchronization barrier.
-- `@:GPU_HOST_DATA(code, use_device_addr=[...])` — Host code with device pointers.
+- `$:END_GPU_PARALLEL_LOOP()` — Required closing for GPU_PARALLEL_LOOP.
+- `$:GPU_LOOP(collapse=N, ...)` — Inner loop within a GPU parallel region.
+- `$:GPU_ENTER_DATA(create=[...])` — Allocate device memory (unscoped).
+- `$:GPU_EXIT_DATA(delete=[...])` — Free device memory.
+- `$:GPU_UPDATE(host=[...])` — Copy device → host (before MPI send).
+- `$:GPU_UPDATE(device=[...])` — Copy host → device (after MPI receive).
+- `$:GPU_ROUTINE(parallelism='[seq]')` — Mark routine for device compilation.
+- `$:GPU_DECLARE(create=[...])` — Declare device-resident data.
+- `$:GPU_ATOMIC(atomic='update')` — Atomic operation on device.
+- `$:GPU_WAIT()` — Synchronization barrier.
+
+Block macros (use `#:call`/`#:endcall`):
+- `GPU_PARALLEL(...)` — GPU parallel region wrapping a code block.
+- `GPU_DATA(copy=..., create=..., ...)` — Scoped data region.
+- `GPU_HOST_DATA(use_device_addr=[...])` — Host code with device pointers.
+
+Block macro usage:
+```
+#:call GPU_PARALLEL(copyin='[var1]', copyout='[var2]')
+  $:GPU_LOOP(collapse=N)
+  do k = 0, n; do j = 0, m
+    ! loop body
+  end do; end do
+  $:END_GPU_LOOP()
+#:endcall GPU_PARALLEL
+```
 
 NEVER write raw `!$acc` or `!$omp` directives. Always use `GPU_*` Fypp macros.
 The precheck source lint will catch raw directives and fail.