v2.8.0 — logging and log viewer UX upgrades

Features

• Expand collector instrumentation with env-gated lifecycle/debug logging and structured sync tracing.
• Improve log viewer interactions with shift-range selection, double-click single selection, and jump-to-latest behavior.
• Add copy-feedback state in Setup Guide code blocks.

Fixes

• Keep log stream behavior intuitive by auto-scrolling only when user remains near the latest entries.
• Continue treating external skill failures as warning-level in viewer.

Docs

• Refresh .env.example with active configuration knobs for collector/logging and frontend refresh.

Chores

• Add app logs paging index migration for stable newest-first queries.
• Bump frontend version to 2.8.0.