P1: align Zig FFI symbol names to the Idris2 ABI

[hyperpolymath]

Problem: ABI ↔ FFI symbol-name drift

The Idris2 ABI in src/interface/abi/Chapeliser/ABI/Foreign.idr is the source of truth for the C-ABI contract. It declares 12 foreign symbols via %foreign "C:c_*, libchapeliser_ffi":

c_init, c_shutdown, c_get_total_items, c_load_item, c_store_result, c_process_item, c_process_chunk, c_reduce, c_is_match, c_key_hash, c_checkpoint_save, c_checkpoint_load

The Zig FFI reference implementation in src/interface/ffi/src/main.zig instead exported these as chapeliser_ref_<stem>. The functions correspond 1:1 by stem and the Result codes already matched, but the symbol names diverged, so the ABI and FFI would not link — every c_* import the ABI declares would resolve to an undefined symbol.

Fix (Zig-only; ABI unchanged because it is the source of truth)

• Renamed the 12 ABI-declared exports from chapeliser_ref_<stem> to exactly c_<stem> in src/interface/ffi/src/main.zig.
• The two extra utility functions (version, build_info) are not part of the ABI, so they are namespaced as chapeliser_version / chapeliser_build_info rather than given c_ names.
• Updated all internal call sites in main.zig tests and the extern fn declarations in src/interface/ffi/test/integration_test.zig to match.

No behaviour or result-code values changed. Only files under src/interface/ffi/ were touched.

Verification

• zig build test (main.zig unit tests, 7/7): pass
• zig build test-integration (links the shared lib, so the test's extern decls resolve against the renamed exports): pass
• idris2 --build chapeliser-abi.ipkg: exit 0
• Cross-check: every C:c_<name> in Foreign.idr now has a matching export fn c_<name> in main.zig; no chapeliser_ref_ references remain.

Note: any rust-ci / Hypatia / governance red checks are pre-existing estate-infra issues unrelated to this Zig-only change.

🤖 Generated with Claude Code

https://claude.ai/code/session_019xMKB3T4Vo5FYC7Czx3JSH

---

Generated by Claude Code