[HackTuah]

Slice 142: Trinity's N6 codec and code registry follow the profile's draft v0.1-r7, and agree with every vector the publisher has cut.

What changes

• Text rule (r7 section 2.4). Text is judged by four tables generated from the Unicode 15.0.0 data files, each checked by SHA-256 (scripts/unicode15_tables.exs, lib/trinity/n6/unicode15.ex). Unassigned code points, format controls (Cf), out-of-order combining marks and NFC quick check No or Maybe are refused. No Unicode normaliser runs anywhere in lib/trinity/n6/; the runtime's Unicode data is never read.
• Decoder order (D0 to D18). A map key's head is checked before its type, an argument's missing bytes before a tag or float refusal, and a container's declared contents against the item limit at its head.
• Body (B1 to B8). One ascending scan over present and required keys. Field types gain ranges, enums, byte bounds, grammars, unions, fixed-shape arrays and nullable fields.
• Header (H1 to H4) and keys (K1 to K3). typ is checked first and selects the label set. New codes header_missing and header_value_invalid; the hash-envelope label set is checked. An Ed25519 key must decode strictly (RFC 8032 section 5.1.3).
• Registry. r7's code names (field_missing, field_type_mismatch, value_out_of_range, text_grammar_mismatch, ...). Each code records the steps that emit it. Only alg_unavailable and the encoder's value_not_n6 are Trinity's own.
• Licence. LICENSES/Unicode-3.0.txt for the embedded tables.

Evidence

• TRINITY_N6_PUBLISHER_VECTORS=<Requisition vectors/n6 at 173487c9> mix test test/trinity/n6/publisher_vectors_test.exs: encoding 347/347, body 124/124, header 85/85, thumbprint 18/18, digest 19/19. The set's SHA384SUMS is checked first. A planted wrong expectation was reported by name.
• On main the same encoding vectors gave 245 of 295 negatives (the text rule and the key-head order).
• TRINITY_UCD_DIR=<UCD 15.0.0> mix test test/trinity/n6/r7_alignment_test.exs: the generator rewrites the module byte for byte. The counts match r7 (Cf 170, NFC_QC No 1,120, Maybe 111, Cn 825,345).
• Trinity's own fixtures are regenerated where a code name changed (scripts/n6_vectors.exs).

Not in this PR: exit 7 for a defect after a verified signature, the small-order Ed25519 rule, and the v3-to-v4 crossing (slice 144).