docs(voyage): S15 — cost-claim truth-pass + premium default-profile pins

Resolve the S14 default-profile contradiction. Investigation overturned
the audit addendum's guess ("code is the bug → balanced"): commit 40d8742
(2026-05-13, "pin all sub-agents to Opus permanently (operator request)")
plus VOYAGE_PROFILE=premium in ~/.zshenv establish premium as the deliberate
default. Operator confirmed in-session: premium is the shipped default; fix
the stale docs, not the code. No code or behaviour changed (lib/ untouched).

Docs (default-name → premium, consistent across resolver + all three docs):
- README + docs/profiles.md + docs/operations.md: 3 lookup-order sites and
  3 profile tables now mark `premium` as the default.
- premium table row corrected to all-opus (matches premium.yaml — a third
  inconsistency the audit missed; README/profiles.md showed opus/sonnet/...).

Cost narrative made honest (premium = all-Opus reality):
- §Cost profile rewritten: uniform model per phase, no orchestrator-vs-swarm
  split; cheaper via --profile balanced/economy.
- Removed false "Sonnet exploration/review swarm" claims (README 195/223/266
  model-neutral; 804 parenthetical; the "Switch the planning model" note).
- profiles.md custom-profile prose corrected: built-in wins over same-named
  custom (findProfilePath), dropping the bogus "balanced is the locked default".

Pins (TDD red→green, doc-consistency.test.mjs):
- default-profile name invariant (resolveProfile ↔ README/profiles/operations)
- profile tables ↔ each built-in yaml phase_models (structural, catches drift)
- cost-claim regression guard (no resurrected Sonnet-swarm phrasing)

S16/S18 surface untouched: counts (23 agents, 9/10 dims, 5/6 dims), versions,
framing gates unchanged. Full suite 686 (684 pass / 2 skip / 0 fail).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LqBYc8Ltrk7LipyJmGxXiB

tests/lib/doc-consistency.test.mjs

@@ -11,6 +11,7 @@ import { readFileSync, readdirSync } from 'node:fs';
 import { join, dirname } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { parseDocument } from '../../lib/util/frontmatter.mjs';
+import { resolveProfile, loadProfile } from '../../lib/profiles/resolver.mjs';
 
 const HERE = dirname(fileURLToPath(import.meta.url));
 const ROOT = join(HERE, '..', '..');
@@ -709,3 +710,79 @@ test('v5.5 — voyage README.md mentions framing enforcement / brief_version 2.2
   assert.ok(t.includes('framing') && t.includes('brief_version 2.2'),
     'voyage README.md must carry a "What\'s new" note for framing enforcement (brief_version 2.2)');
 });
+
+// --- S15 — default-profile name + per-phase model claims (cost-claim truth-pass) ---
+// The resolver's hardcoded default (lib/profiles/resolver.mjs) is the single
+// source of truth for which built-in profile a fresh user gets. README,
+// docs/profiles.md, and docs/operations.md must all mark THAT profile as the
+// default and must not mark any other built-in as default. Guards the
+// code-vs-docs contradiction the S14 audit surfaced (Addendum finding #3).
+const PROFILE_DOCS = ['README.md', 'docs/profiles.md', 'docs/operations.md'];
+
+test('S15: default-profile name is consistent across resolver + all profile docs', () => {
+  // Empty env so the operator's VOYAGE_PROFILE does not mask the hardcoded default.
+  const { profile: def, profile_source } = resolveProfile({}, {});
+  assert.equal(profile_source, 'default', 'resolveProfile({}, {}) must report source=default');
+  assert.equal(def, 'premium', 'resolver hardcoded default is premium (operator decision 2026-05-13, commit 40d8742)');
+
+  const OTHERS = ['economy', 'balanced', 'premium'].filter((p) => p !== def);
+  for (const doc of PROFILE_DOCS) {
+    const body = read(doc);
+    assert.ok(
+      body.includes(`\`${def}\` (default)`),
+      `${doc}: profile table must mark \`${def}\` as "(default)" to match resolver`,
+    );
+    for (const other of OTHERS) {
+      assert.ok(
+        !body.includes(`\`${other}\` (default)`),
+        `${doc}: must NOT mark \`${other}\` as "(default)" — resolver default is ${def}`,
+      );
+      assert.ok(
+        !body.includes(`Default \`${other}\``),
+        `${doc}: lookup-order must not say "Default \`${other}\`" — resolver default is ${def}`,
+      );
+    }
+  }
+});
+
+test('S15: profile tables encode each built-in yaml phase_models exactly', () => {
+  // Column order in every profile table: Profile | Brief | Research | Plan | Execute | Review | Continue | Use case
+  const PHASES = ['brief', 'research', 'plan', 'execute', 'review', 'continue'];
+  for (const name of ['economy', 'balanced', 'premium']) {
+    const pm = loadProfile(name).phase_models; // {brief:'opus', ...}
+    const expected = PHASES.map((ph) => pm[ph]);
+    for (const doc of PROFILE_DOCS) {
+      const row = read(doc)
+        .split('\n')
+        .find((l) => new RegExp(`^\\|\\s*\`${name}\``).test(l));
+      assert.ok(row, `${doc}: profile table is missing a \`${name}\` row`);
+      const cells = row.split('|').map((c) => c.trim());
+      // cells[0] is '' (leading pipe), cells[1] is the name, cells[2..7] are the 6 models
+      const docModels = cells.slice(2, 8);
+      assert.deepEqual(
+        docModels,
+        expected,
+        `${doc}: \`${name}\` row models ${JSON.stringify(docModels)} must equal lib/profiles/${name}.yaml ${JSON.stringify(expected)}`,
+      );
+    }
+  }
+});
+
+test('S15: README cost prose does not resurrect the false Sonnet-swarm claim', () => {
+  // All 24 sub-agents are model: opus (operator-pinned, commit 40d8742) and the
+  // model is uniform per phase — there is no "Opus orchestrates / Sonnet runs
+  // the swarms" split. These phrases asserted the false split and must stay out.
+  const md = read('README.md');
+  const BANNED = [
+    'Sonnet exploration',
+    'Sonnet runs the exploration',
+    'front-loads cheap Sonnet',
+    'exploration agents stay on Sonnet',
+  ];
+  for (const phrase of BANNED) {
+    assert.ok(
+      !md.includes(phrase),
+      `README.md must not claim "${phrase}" — sub-agents are opus-pinned; default profile runs Opus on every phase`,
+    );
+  }
+});