[dmitrii-f-t27]

Closes #12573

What

Ports crates/trios-rainbow-bridge/src/merkle.rs (gHashTag/trios at 78671ba79482, 103 lines) to specs/port/trios/crates/trios-rainbow-bridge/src/merkle.t27, roadmap stage 6 (goal #4548).

Seven functions under the names the issue lists: MerkleChain_new, MerkleChain_root, MerkleChain_root_hex, MerkleChain_len, MerkleChain_is_empty, MerkleChain_append, hex_encode.

Ported decision, not plumbing

• MerkleChain_append takes the resulting digest instead of &RainbowEvent: serialising the event and hashing root || bytes with blake3 is the caller's side of the boundary.
• hex_encode writes into a fixed 64-byte buffer instead of allocating a String: .t27 in this corpus has no allocator, and the chain root is the only caller (line 34).
• Both deviations are named in the file header.

Acceptance criteria (run from the repository root)

#	command	result
1	test -f specs/port/trios/crates/trios-rainbow-bridge/src/merkle.t27	present
2	grep of the seven function names	7
3	t27c gen ... | grep -c 'not yet implemented' / | wc -l	0 / 158
4	t27c spec-status ...	IMPLEMENTED
5	grep of test blocks	9
6	t27c test-report ... | grep -c BLOCKED	0

t27c test-report: 9 tests, 9 pass, 0 FAIL, 0 vacuous (34+3+3+1+2+64+6+4+5 runtime asserts).

Seal

t27c seal --save produced .trinity/seals/src_port::trios::crates::trios_rainbow_bridge::src::merkle.json:

• spec_path = specs/port/trios/crates/trios-rainbow-bridge/src/merkle.t27
• spec_hash = sha256:ab3c433363935a7b20e5b59f6ef1cd7be3925f6ce8b1095f985a6ec3db084b88 (recomputed and matched)
• tests = {passed: 9, total: 9, failed: 0, vacuous: 0}

Boundary

The spec plus its generated seal. No other spec, no scratch file, no edit to the original.

Not verified

t27c gen-rust output for this spec was not compiled against the trios crate; the generated Rust is not wired into crates/trios-rainbow-bridge by this PR.

[dmitrii-f-t27]

Red non-required checks: neither is this PR

• gate-topology (run 41115018037): fails on NOT CLASSIFIED (1, ceiling 23): stale-arm-repair.yml. This PR touches no workflow. The same check is red on the recent merged PRs t27b: the zero test is one word -- CBZ/CBNZ carry a compare against zero and its branch (Refs #12871) #12896, t27b: the typed-lane constant fold takes its value from the arithmetic law (Refs #12871) #12893 and t27b: bless the ledger from run 4125e2902 -- green ratchet #12856, and it passed on master at 16:06 with the same 82de5086 tip — repository state, not this diff.
• t27b-native-macos (run 41115018660): the job conclusion is cancelled, not failed. Its sibling t27b-native-linux is green and t27b-native-ratchet is still running. No Rust source is touched here.

Required checks are green: validate, check-linked-issue, parse-ratchet, own-language.

Self-check of the diff: two added files (the spec and its seal), nothing else; git status --short on the branch shows exactly those two.