FEAT-133: Add gateway diagnostics logging with UI

[shafty023]

• Add GatewayLogger class with info/warn/error/debug levels and in-memory ring buffer (500 entries) for UI display
• Add structured logging to Socket.IO lifecycle (connect, disconnect, auth errors, hello ack, hello timeout)
• Add logging to cloud command executor (enqueue, execute, gateway HTTP errors, timeout, failure)
• Add logging to symphony loop harness (request source relay/local, process spawn, exit code, event POST errors, artifact upload errors)
• Split logging: lifecycle events and errors always visible, granular per-step details gated behind verbose toggle
• Suppress consecutive identical log messages (dedup presence spam)
• Add Diagnostics tab with auto-refresh, verbose toggle, and color-coded error/warn row highlighting
• Rename Activity Log tab to Requests for clarity
• Add verboseLogging to DesktopSettings with persistence

Testing:

• just desktop-typecheck passes
• just desktop-test passes (288/288)
• just desktop-lint passes

Risks:

• Logging adds minor overhead to hot paths (suppressed by dedup)
• In-memory buffer capped at 500 entries, no disk persistence

[closedloop-ai-stage]

Code Review Summary

Status: Approved

Reviewers: Bug Hunter A, Bug Hunter B, Unified Auditor, Premise Reviewer, Cloud Command Executor Specialist

Findings

Severity	Count
Blocking	0
High	0
Medium	5

MEDIUM Issues (consider)

1. [[P3] [apps/desktop/src/renderer/index.html:2825] LOG_LEVEL_COLORS constant defined but never used
2. [[P2] [apps/desktop/src/main/gateway-logger.ts:60] clear() does not reset lastMessage, causing first post-clear duplicate to be silently dropped
3. [[P2] [apps/desktop/src/renderer/index.html:2852] e.tag rendered without HTML escaping in logsList innerHTML
4. [[P2] [apps/desktop/src/renderer/index.html:2855] renderLogs unconditionally scrolls to bottom on every auto-refresh, disrupting user reading position
5. [[P2] [apps/desktop/src/main/gateway-logger.ts:62] clear() passes live mutable buffer reference to onChange, inconsistent with log() which passes a copy

Validation Stats

• Agent failures: 0 partitions skipped
• Cross-file grouped: 0 findings consolidated
• Duplicates merged: 2

Recommendation: Approve. No blocking or high issues. The clear()/lastMessage bug and scroll-lock UX are the most impactful medium items.