test(evals): Voyage's fixed test set as a plugin eval suite, expectations written before the first run

Seven `claude plugin eval` cases under evals/, runs: 1, deterministic graders
only (regex, tool_used, file_exists), no ablation. Each case tests one thing
Voyage promises and stops within minutes, headless:

- plan-requires-brief, plan-project-not-initialized, plan-rejects-unknown-export,
  review-requires-project: argument guards stop before any Agent or Write.
- plan-halts-without-phase-signals: a brief_version 2.1 brief without
  phase_signals halts /trekplan at the sequencing gate, before the swarm.
- review-validate-flags-bad-finding-id (known-positive) and
  review-validate-passes-clean-review (known-negative): /trekreview --validate
  names REVIEW_BAD_FINDING_ID on a planted bad ID and stays clean on a valid file.

Each case's expected_outcome is committed here, before the suite has run.
Fixtures are written by an inline scaffold.sh (needs --scaffold): chose inline
heredocs because a run cannot read the eval directory, and the add_dirs path
mapping is not documented. evals/results/ is ignored.

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

evals/plan-halts-without-phase-signals/scaffold.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# Seeds the empty run workspace with a project folder whose brief declares
+# brief_version 2.1 but carries neither phase_signals nor phase_signals_partial.
+# Self-contained on purpose: the run cannot read the eval directory.
+set -eu
+mkdir -p proj
+cat > proj/brief.md <<'BRIEF'
+---
+type: trekbrief
+brief_version: "2.1"
+created: 2026-09-23
+task: "Eval fixture: add a greeting helper"
+slug: eval-greeting
+project_dir: proj/
+research_topics: 0
+research_status: skipped
+auto_research: false
+interview_turns: 1
+source: fixture
+---
+
+# Task: add a greeting helper
+
+## Intent
+
+Eval fixture for the Voyage proevesett. Not a real task.
+
+## Goal
+
+A function `greet(name)` returns `Hello, <name>!`.
+
+## Success Criteria
+
+- `greet("Ada")` returns `Hello, Ada!`.
+BRIEF