fix(worker): gate mcp discovery cache diagnostics

[zebbern]

Summary

• route MCP discovery cache success diagnostics through workflowDiagnosticLog
• keep cache behavior and Redis TTL unchanged
• add a focused regression test proving successful cache writes stay quiet by default

Verification

• bun test worker/src/temporal/activities/tests/mcp-discovery.activity.test.ts
• bun test worker/src/temporal/activities
• bun test worker
• bun run typecheck
• bun run lint
• bun run test

[Copilot]

Pull request overview

This PR reduces noisy worker logs by routing MCP discovery cache “success” diagnostics through the existing workflowDiagnosticLog() gate (enabled via SENTRIS_DEBUG_WORKFLOW=1), while keeping the Redis cache format and TTL unchanged.

Changes:

• Replace unconditional console.log on successful MCP discovery cache writes with workflowDiagnosticLog().
• Add a regression test that proves successful cache writes do not call console.log by default.
• Keep the Redis key format and 5-minute TTL (setex(..., 300, ...)) unchanged.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
worker/src/temporal/activities/mcp-discovery.activity.ts	Gates the “cached discovery results” success log behind workflowDiagnosticLog() instead of always emitting to stdout.
worker/src/temporal/activities/__tests__/mcp-discovery.activity.test.ts	Adds a focused test with a mocked Redis client to ensure no default console.log output on successful cache writes.

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