feat: show dashboard URL on startup and add lore logs command

[BYK]

Summary

• Surface the dashboard URL (http://host:port/ui) in all startup messages (lore run, lore start, OpenCode plugin) so users know the UI exists
• Add a persistent file-based log sink in core/log.ts that captures all log.info/warn/error calls to ~/.local/share/opencode-lore/lore.log regardless of LORE_DEBUG, with 5MB rotation
• Add lore logs CLI command with -f (follow), -n (line count), and --path flags

Closes #242

Details

Dashboard URL notification

Added [lore] Dashboard: <url>/ui messages after existing "gateway listening" lines in:

• packages/gateway/src/cli/run.ts — both owned and reused gateway paths
• packages/gateway/src/cli/start.ts — both "already running" and fresh start paths
• packages/opencode/src/index.ts — OpenCode plugin stderr banner

Persistent log file

All log.info/warn/error calls now write to ~/.local/share/opencode-lore/lore.log regardless of LORE_DEBUG:

• ISO 8601 timestamps with level tags: 2025-01-15T14:32:05.123Z [INFO ] message
• Single-file rotation at 5MB (.log.1 backup, ~10MB max disk)
• Rotation check every 1000 writes, not every write
• Disabled during tests (NODE_ENV=test)
• Silently degrades on any I/O error

lore logs command

Usage	Behavior
lore logs	Print last 50 lines and exit
lore logs -f	Follow log output in real-time (300ms poll)
lore logs -n 100	Print last 100 lines
lore logs --path	Print log file path and exit