fed-sx-m1: Step 4d — bootstrap:build_genesis/verify_genesis + cidhash helpers + 12 tests

plans/fed-sx-milestone-1.md

@@ -251,7 +251,7 @@ replay(LogState, InitAcc, Fun) -> ...
 - [x] **4b-vld** — Validators: envelope-shape, signature, type-schema — 3 `DefineValidator` files + manifest updated + 5 new parse tests
 - [x] **4b-cod** — Codecs (dag-cbor, raw, dag-json) + sig-suites (rsa-sha256-2018, ed25519-2020) + audience predicates (Public, Followers, Direct) — 8 SX files + manifest fully populated + 14 new parse tests
 - [x] **4c** — `bootstrap:read_genesis/0,1` + `read_section/2` + `sections/0` + `section_subdir/1` + `ends_with_sx/1` in Erlang: walk seven hardcoded section subdirs, filter `.sx` files via byte-pattern suffix match, read each into a binary. Returns `{ok, [{Section, [{Name, Bytes}, ...]}, ...]}`. Skips SX parsing — the substrate has no in-Erlang binary→SX-term path (same gap as Step 3b); bundle CID over raw bytes is enough for Step 4d. `next/tests/bootstrap_read.sh` (15 cases).
-- [ ] **4d** — `bootstrap:build_genesis/1` + `bootstrap:verify_genesis/1`: compute bundle CID over the read forms via the host `cid:to_string` substrate; verify against a stored `bundle.cidhash`
+- [x] **4d** — `bootstrap:build_genesis/1` + `verify_genesis/2` + `cidhash_path/1` + `write_cidhash/2` + `read_cidhash/1`: bundle CID via host `cid:to_string` over `{genesis_bundle, Sections}`; mismatch returns `{error, {cid_mismatch, Got, Expected}}`; `.cidhash` sibling file persists between runs. `next/tests/bootstrap_build.sh` (12 cases).
 - [ ] **4e** — `bootstrap:load_genesis/1`: register parsed definitions into the in-memory registry (depends on Step 5)
 
 **Deliverables:**
@@ -955,6 +955,7 @@ A few things still under-specified; resolve as work begins.
 Newest first. One line per sub-deliverable commit. Erlang conformance gate
 (`bash lib/erlang/conformance.sh`) must remain 729/729 on every entry.
 
+- **2026-05-28** — Step 4d: `bootstrap:build_genesis/1` + `verify_genesis/2` + `.cidhash` helpers in `next/kernel/bootstrap.erl`. Bundle CID delegated to host `cid:to_string` over `{genesis_bundle, Sections}` — deterministic, ~59 byte CIDv1 binary. `verify_genesis/2` returns `ok` on match, `{error, {cid_mismatch, Got, Expected}}` on drift. `write_cidhash`/`read_cidhash` persist the CID to a `.cidhash` sibling file (path hand-spelled `<<...,47,46,99,...>>` per the string-literal-in-binary substrate quirk). `next/tests/bootstrap_build.sh` 12/12. Erlang conformance 729/729.
 - **2026-05-27** — Step 4c: `next/kernel/bootstrap.erl` — Erlang module that enumerates the genesis bundle by walking seven hardcoded section subdirs via `file:list_dir/1`, filters `.sx` files via byte-pattern suffix match (`ends_with_sx/1`), reads each into a binary via `file:read_file/1`. Returns `{ok, [{Section, [{Name, Bytes}, ...]}]}`. Hits the same SX-parser substrate gap as Step 3b — kept the surface byte-only; parsing happens via SX-side helpers in later steps. Port gotchas: `fun name/arity` references unsupported (use anonymous fun wrappers); `<<"...">>` string-literal segments truncate to one byte (paths hand-spelled as integer-segment binaries). `next/tests/bootstrap_read.sh` 15/15. Erlang conformance 729/729.
 - **2026-05-27** — Step 4b-cod: bootstrap codecs + sig-suites + audience predicates complete. 3 `DefineCodec` files (dag-cbor + raw + dag-json, dag-cbor + dag-json deferring to host-codec primitive when wired), 2 `DefineSigSuite` files (rsa-sha256-2018 PEM-keyed, ed25519-2020 multibase-keyed, both :verify returning false as m2-deferred stand-in), 3 `DefineAudience` files (Public/Followers/Direct member-of predicates per design §16). Manifest now lists 26 bootstrap files across all eight sections; `next/tests/genesis_parse.sh` 50/50. Step 4b complete; remaining Step 4 is bundler code (4c–4e). Erlang conformance 729/729.
 - **2026-05-27** — Step 4b-vld: bootstrap validators complete — 3 `DefineValidator` SX files (envelope-shape mirroring Step 2a, signature stub delegating to envelope:verify_signature/2 per design §9.6, type-schema looking up the object-type schema from define-registry). Manifest `:validators` populated; `next/tests/genesis_parse.sh` 36/36. Erlang conformance 729/729.