feat(params): support real(stp) declarations in Fortran codegen

[sbryngelson]

Summary

Two small follow-ups on top of #1456 (auto-generated Fortran namelists/decls).

1. real(stp) support in the parameter codegen

After #1456, every REAL parameter the generator emits is hardcoded to real(wp) (fortran_gen.py's _FORTRAN_TYPES). That's correct for the current parameter set — every generated scalar/array is computation-side wp, and true storage-precision (stp) field data is a derived type / allocatable that the generator deliberately excludes. But there was no way to make the generator emit real(stp) if a future scalar or FORTRAN_ARRAY_DIMS array genuinely needed it — it would silently get wp.

This adds an explicit, declarable escape hatch:

• ParamDef.storage_precision: bool = False
• fortran_type_decl honors it for REAL/ANALYTIC_REAL → real(stp) (covers both scalar and array paths)
• _r(..., storage_precision=True) threads it through

Behavior-preserving for the current parameter set: generated output is byte-identical (all reals remain real(wp), no stp leaks). Verified via the full params_tests suite (126 passed) plus a new test_fortran_type_real_storage_precision.

Known limitation (inherent): a REAL param still defaults to wp; this can't detect unstated intent. The only alternative — a hardcoded must-be-stp name list — is circular. So defaulting to wp with an explicit opt-in is the right floor.

2. Agent-guidance docs: correctness + slimming

CLAUDE.md and .claude/rules/* are all auto-loaded into agent context every turn, so accuracy and non-duplication matter. This pass:

• Fixes a wrong formula: buff_size was documented as 2*weno_polyn + 2 (only the viscous-WENO case); corrected to the real per-scheme set (WENO/MUSCL/IGR + Lagrange/IB floors) with a pointer to s_configure_coordinate_bounds.
• Fixes misdirection: runtime-validation guidance pointed at m_checker.fpp files whose s_check_inputs are empty for pre/post; rewrote it to say where a check actually runs (shared → m_checker_common.fpp, sim-only → simulation/m_checker.fpp, pre/post-only → their files).
• Slims + dedupes: trims reference enumerations (Commands cheat-sheet, GPU-macro list, #ifdef tail) to essentials + source-of-truth pointers; collapses the duplicated wp/stp definition to one home; adds a Working Style section pointing at the karpathy-guidelines skill; fixes the stale "6 checks" → "7 checks" count. No enforceable rule or domain fact removed.

Test plan

• ./mfc.sh format -j 8 (no changes)
• params_tests: 126 passed (incl. new stp test)
• Generated decls confirmed byte-identical for existing params
• doc claims verified against source (buff_size, empty pre/post checkers)
• pre-commit precheck hook passed on every commit
• Full ./mfc.sh precheck -j 8 / CI

[qodo-code-review]

Qodo reviews are paused for this user.

Troubleshooting steps vary by plan Learn more →

On a Teams plan?
Reviews resume once this user has a paid seat and their Git account is linked in Qodo.
Link Git account →

Using GitHub Enterprise Server, GitLab Self-Managed, or Bitbucket Data Center?
These require an Enterprise plan - Contact us
Contact us →