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/fixtures/baseline-all-a/.mcp.json

@@ -3,8 +3,7 @@
     "memory": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-memory"],
-      "trust": "workspace"
+      "args": ["-y", "@modelcontextprotocol/server-memory"]
     }
   }
 }

tests/fixtures/healthy-project/.mcp.json

@@ -3,14 +3,12 @@
     "memory": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-memory"],
-      "trust": "workspace"
+      "args": ["-y", "@modelcontextprotocol/server-memory"]
     },
     "filesystem": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-filesystem", "./docs"],
-      "trust": "trusted"
+      "args": ["-y", "@modelcontextprotocol/server-filesystem", "./docs"]
     }
   }
 }

tests/fixtures/marketplace-large/.mcp.json

@@ -3,20 +3,17 @@
     "memory": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-memory"],
-      "trust": "workspace"
+      "args": ["-y", "@modelcontextprotocol/server-memory"]
     },
     "filesystem": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-filesystem", "./docs"],
-      "trust": "trusted"
+      "args": ["-y", "@modelcontextprotocol/server-filesystem", "./docs"]
     },
     "github": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-github"],
-      "trust": "trusted"
+      "args": ["-y", "@modelcontextprotocol/server-github"]
     }
   }
 }

tests/fixtures/marketplace-medium/.mcp.json

@@ -3,8 +3,7 @@
     "memory": {
       "type": "stdio",
       "command": "npx",
-      "args": ["-y", "@modelcontextprotocol/server-memory"],
-      "trust": "workspace"
+      "args": ["-y", "@modelcontextprotocol/server-memory"]
     }
   }
 }