fix(approval): approval commits carry the caller's Co-Authored-By trailer

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/HANDOVER-CONTRACTS.md

@@ -112,7 +112,7 @@ Optional but standard sections: `## Non-Goals`, `## Constraints`, `## Preference
 
 **Intent approval gate (veikart steg 1) — additive schema, consumer-side requirement.** The two `intent_approved_*` fields are additive and optional in the schema: `brief-validator.mjs` does not require them, `/trekresearch` does not read them, and no `brief_version` bump is involved. The requirement lives in `/trekplan` Phase 1 (`### Read the brief`), which runs `intent-approval.mjs --check` and **halts** on `BRIEF_INTENT_NOT_APPROVED` (no marker), `BRIEF_INTENT_APPROVAL_STALE` (`## Intent` or `## Goal` changed after approval) or `BRIEF_INTENT_APPROVAL_INVALID` (malformed marker, or a section missing, empty or present more than once; a `## ` line inside a code block or HTML comment is not a heading). It is version-independent, so a brief from ANY producer, of any `brief_version`, stops at `/trekplan` until approved. No producer has to emit anything new: the operator approves through `/trekbrief --approve <project-dir | brief-file>`, a Voyage-side step open to every producer's brief, whether it is planned with `--project` (`<dir>/brief.md`) or `--brief <file>`, so no producer is privileged. `trekreview` briefs are exempt. The exemption is read from the brief's own frontmatter, so relabelling a brief `type: trekreview` walks past the gate, the same trust class as self-stamping. **What the marker does not prove:** same user, same machine. Any session can run `--stamp`. The marker is a trace that the approval step ran against this exact text, not a signature (see the header of `lib/validators/intent-approval.mjs`). `--stamp` also emits `brief-approved` to `trekexecute-stats.jsonl` under `CLAUDE_PLUGIN_DATA`, falling back to the plugin data dir the yardstick reads, on both the manual and the auto path.
 
-**Approval log (K2) — consumer-side requirement, no schema change.** After the stamp, `/trekbrief` appends the approval to the target repo's log with `lib/util/approval-log.mjs append --kind intent --subject <brief> --sha256 <intent hash>` and commits it with `lib/util/artifact-commit.mjs` (the log always; the brief too when `artifact_store: git`). The log (`.claude/voyage/approvals.jsonl`, read and written only by that CLI) is append-only and hash-chained: each record carries `seq`, `ts`, `kind` (`intent | plan | review | merge | release`), `subject`, the content's `sha256`, an optional `expires`, `prev` and its own `hash`. `/trekplan` Phase 1 runs `approval-log.mjs verify --kind intent --subject <brief> --sha256 <intent_approved_hash>` after the marker check and halts on `broken` (a record edited, removed or reordered), `diverged` (the committed log is no longer a prefix of the file), `not-logged` or `mismatch`; exit 2 (could not run) halts too. A brief approved before the log existed is `not-logged`: the remedy is the same `/trekbrief --approve`, open to every producer's brief. Only an explicit "Approve" counts: `approval-log.mjs answer` refuses «høres bra ut», «gjør som du vil» and an empty answer. Trust limits are those of the marker (same user, same machine; a trace, not a signature); what the log adds is that each approval is a commit in `git log`, and that a committed approval cannot be rewritten without `diverged`. Adapted from bashebr/ai-native-sdlc@11fb8d7 (MIT), corrected so the approval is bound to content and cannot be written unseen.
+**Approval log (K2) — consumer-side requirement, no schema change.** After the stamp, `/trekbrief` appends the approval to the target repo's log with `lib/util/approval-log.mjs append --kind intent --subject <brief> --sha256 <intent hash>` and commits it with `lib/util/artifact-commit.mjs` (the log always; the brief too when `artifact_store: git`). The commit carries the caller's trailer: every call passes `--trailer "Co-Authored-By: Claude {model} <noreply@anthropic.com>"` with `{model}` filled in, and the CLI refuses (exit 1, nothing committed) a missing trailer, a multi-line one, one that does not read `Co-Authored-By: <name> <<email>>` (an unfilled `{model}` included) and one holding `Claude-Session:`; a bad `--store` stays exit 2 and is checked first. The log (`.claude/voyage/approvals.jsonl`, read and written only by that CLI) is append-only and hash-chained: each record carries `seq`, `ts`, `kind` (`intent | plan | review | merge | release`), `subject`, the content's `sha256`, an optional `expires`, `prev` and its own `hash`. `/trekplan` Phase 1 runs `approval-log.mjs verify --kind intent --subject <brief> --sha256 <intent_approved_hash>` after the marker check and halts on `broken` (a record edited, removed or reordered), `diverged` (the committed log is no longer a prefix of the file), `not-logged` or `mismatch`; exit 2 (could not run) halts too. A brief approved before the log existed is `not-logged`: the remedy is the same `/trekbrief --approve`, open to every producer's brief. Only an explicit "Approve" counts: `approval-log.mjs answer` refuses «høres bra ut», «gjør som du vil» and an empty answer. Trust limits are those of the marker (same user, same machine; a trace, not a signature); what the log adds is that each approval is a commit in `git log`, and that a committed approval cannot be rewritten without `diverged`. Adapted from bashebr/ai-native-sdlc@11fb8d7 (MIT), corrected so the approval is bound to content and cannot be written unseen.
 
 **Failure modes:**
 - `BRIEF_INTENT_NOT_APPROVED` / `BRIEF_INTENT_APPROVAL_STALE` / `BRIEF_INTENT_APPROVAL_INVALID` → `/trekplan` halts (intent-approval gate, above); remedy `/trekbrief --approve <project-dir | brief-file>`