fix(mcp-config-validator): remove invented trust field (verify-first)

`.mcp.json` has no per-server `trust` key — verified 2026-06-18 against
code.claude.com/docs/en/mcp + /settings. MCP server approval is
dialog/settings-based (enableAllProjectMcpServers / enabledMcpjsonServers /
disabledMcpjsonServers), never a JSON field. The scanner's "Missing trust
level" (CA-MCP-001, medium) and "Invalid trust level" (high) were false
positives flagging a field that does not exist.

- scanner: delete both trust checks + VALID_TRUST_LEVELS; drop `trust` from
  VALID_SERVER_FIELDS so a stray `trust` is now flagged as an unknown field
- humanizer: remove the two trust-level entries
- knowledge (5 files): point to the real approval mechanism, not a trust field
- fixtures: scrub `trust` (incl. the invalid "local" in optimal-setup)
- tests: flip assertions (no trust-level finding; stray trust -> unknown
  field) + add knowledge-staleness re-freeze guards
- snapshots: reseed (marketplace-medium .mcp.json -8 tokens, hermetic)
- gap-matrix: mark the trust verify-first item DONE

Suite: 853/853 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ter3E2JSi1Khgmuf2kady8

tests/scanners/mcp-config-validator.test.mjs

@@ -81,13 +81,9 @@ describe('MCP scanner — broken project', () => {
     assert.equal(unknown.severity, 'high');
   });
 
-  it('detects missing trust level', () => {
-    assert.ok(result.findings.some(f => f.title.includes('Missing trust level')));
-  });
-
-  it('missing trust is medium severity', () => {
-    const trust = result.findings.find(f => f.title.includes('Missing trust level'));
-    assert.equal(trust.severity, 'medium');
+  it('does NOT flag any trust level — `trust` is not a real .mcp.json field (CC docs verified 2026-06-18)', () => {
+    assert.ok(!result.findings.some(f => /trust level/i.test(f.title)),
+      'no "Missing trust level"/"Invalid trust level" findings: the field does not exist in the official schema');
   });
 
   it('detects unreferenced env vars in args', () => {
@@ -103,6 +99,43 @@ describe('MCP scanner — broken project', () => {
   });
 });
 
+describe('MCP scanner — stray `trust` field is an unknown field (verify-first, 2026-06-18)', () => {
+  let result;
+  let tmpRoot;
+
+  beforeEach(async () => {
+    resetCounter();
+    tmpRoot = await mkdtemp(join(tmpdir(), 'ca-mcp-trust-'));
+    // `trust` is NOT a field in the official .mcp.json schema (verified against
+    // code.claude.com/docs/en/mcp + /settings, 2026-06-18). Approval is
+    // dialog/settings-based (enableAllProjectMcpServers / enabledMcpjsonServers /
+    // disabledMcpjsonServers), never a per-server JSON field.
+    const mcp = {
+      mcpServers: {
+        legacy: { type: 'stdio', command: 'node', args: ['server.mjs'], trust: 'workspace' },
+      },
+    };
+    await writeFile(join(tmpRoot, '.mcp.json'), JSON.stringify(mcp, null, 2) + '\n', 'utf8');
+    const discovery = await discoverConfigFiles(tmpRoot);
+    result = await scan(tmpRoot, discovery);
+  });
+
+  afterEach(async () => {
+    if (tmpRoot) await rm(tmpRoot, { recursive: true, force: true });
+  });
+
+  it('flags `trust` as an unknown MCP server field', () => {
+    const f = result.findings.find(x => x.title.includes('Unknown MCP server field')
+      && /trust/.test(x.description || ''));
+    assert.ok(f, 'a `trust` field must now be reported as an unknown field');
+  });
+
+  it('emits no "trust level" findings at all', () => {
+    assert.ok(!result.findings.some(x => /trust level/i.test(x.title)),
+      'the invented trust-level checks must be gone');
+  });
+});
+
 describe('MCP scanner — env-var false positives (CC 2.1.139/2.1.142, Batch 1)', () => {
   let tmpRoot;
   let envFindings;
@@ -118,13 +151,11 @@ describe('MCP scanner — env-var false positives (CC 2.1.139/2.1.142, Batch 1)'
           // CLAUDE_PROJECT_DIR is auto-injected (CC 2.1.139); ${VAR%…}/${VAR:-…}
           // are POSIX expansions CC resolves (2.1.142) — none need an env block.
           args: ['${CLAUDE_PROJECT_DIR}/server.mjs', '--root', '${HOME%/}', '--cfg', '${CONFIG_DIR:-/etc}'],
-          trust: 'workspace',
         },
         legacy: {
           type: 'stdio',
           command: 'node',
           args: ['${REAL_MISSING}'],
-          trust: 'workspace',
         },
       },
     };