feat(mcp): single-connector default set + connector policy (#2219)

Reduce the default .mcp.json to one connector (chrome-devtools) per the
new policy in docs/MCP-CONNECTOR-POLICY.md: a default earns its slot only
if it is universal AND MCP beats a CLI/API wrapped in a skill. June 2026
audit verdicts: github -> gh via github-ops skill; context7 -> REST via
documentation-lookup; exa -> harness-native search (+ exa-search skill);
memory -> native harness memory + instincts; playwright -> playwright CLI
skills (vendor moved agent flows off MCP); sequential-thinking -> native
extended thinking. All six remain opt-in in mcp-configs/mcp-servers.json.
Tests updated: plugin-manifest policy assertions + install-apply Cursor
expectations.

Co-authored-by: ECC Test <ecc@example.test>

.codex-plugin/README.md

@@ -49,12 +49,9 @@ stay below provider length limits.
 
 | Server | Purpose |
 |---|---|
-| `github` | GitHub API access |
-| `context7` | Live documentation lookup |
-| `exa` | Neural web search |
-| `memory` | Persistent memory across sessions |
-| `playwright` | Browser automation & E2E testing |
-| `sequential-thinking` | Step-by-step reasoning |
+| `chrome-devtools` | Interactive browser debugging via Chrome DevTools (CDP sessions, performance traces, console/network inspection) |
+
+The former defaults (`github`, `context7`, `exa`, `memory`, `playwright`, `sequential-thinking`) were retired in the June 2026 connector audit — their jobs are covered by skills wrapping CLIs/REST APIs or by harness-native features. They remain available as opt-in entries in `mcp-configs/mcp-servers.json`. See `docs/MCP-CONNECTOR-POLICY.md` for the policy and the per-connector rationale.
 
 ## Notes