Read-side fix dual to fldloadop: signed-narrow local/global ident loads
now MOVSXD/MOVSWQ/MOVSBQ from the slot instead of raw MOVQ. Deref-stores
(MOVL/MOVW/MOVB) no longer corrupt downstream i64 widens. Compound RMW
restructured to gate direct-mem ADDQ/SUBQ on load_op == MOVQ. Top-level
lets use LEAQ+indirect (w6a doesn't expose MOVSXD/MOVSWQ/MOVSBQ for
D_EXTERN).
dotchainresolve out-params restored to natural *i32 (workaround retired).
selfhost/CLAUDE.md graduated.
type_isunsigned recurses TY_ENUM and includes TY_RUNE on both stages.
13 LOAD + 6 STORE ladder sites (cstage) plus 4 more wwstage stragglers
in cgindex/cgforrange collapsed to fldloadop/fldstoreop helpers. N_CAST
narrow gate symmetrised; task #1's literal-kind workaround retired.
bool kept out of type_isunsigned, special-cased in field helpers.
Retroactively fixes a u32 mis-sign-extend in deref-compound (sz=4
hardcoded MOVSXD), pinned by new 660_field_signed row.