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/snapshots/default-output/scan-orchestrator.json

@@ -481,7 +481,7 @@
           },
           {
             "source": ".mcp.json",
-            "estimated_tokens": 53,
+            "estimated_tokens": 45,
             "rank": 5,
             "recommendations": [
               "Deduplicate overlapping entries — each duplicate inflates the per-turn schema payload.",
@@ -490,7 +490,7 @@
             "path": "/Users/ktg/repos/ktg-plugin-marketplace/config-audit/tests/fixtures/marketplace-medium/.mcp.json"
           }
         ],
-        "total_estimated_tokens": 809,
+        "total_estimated_tokens": 801,
         "activeConfig": {
           "claudeMdEstimatedTokens": "<ANCESTOR_DERIVED>",
           "mcpServerCount": 1,

tests/snapshots/default-output/token-hotspots.json

@@ -5,7 +5,7 @@
     "status": "ok",
     "files_scanned": 2,
     "duration_ms": 0,
-    "total_estimated_tokens": 809,
+    "total_estimated_tokens": 801,
     "hotspots": [
       {
         "source": "mcp:memory (.mcp.json)",
@@ -47,7 +47,7 @@
       },
       {
         "source": ".mcp.json",
-        "estimated_tokens": 53,
+        "estimated_tokens": 45,
         "rank": 5,
         "recommendations": [
           "Deduplicate overlapping entries — each duplicate inflates the per-turn schema payload.",