Issue #48: Advice window styling, operator timing, rules, UI consistency

[erikdarlingdata]

Summary

• Expensive operators: Multi-line format with both CPU and elapsed timing, node IDs for cross-referencing, fix for transparent operator CPU subtraction
• New Rule 31: Parallel Wait Bottleneck — fires when elapsed >> CPU in parallel plans
• Rule 25: Tightened Ineffective Parallelism threshold to 0.8–1.3
• Warning formatting: Structured multi-line format with bullet stats for filter/lookup/predicate warnings; U+001F encoding to preserve internal newlines through line splitter
• Advice window: SelectableTextBlock for copy/paste, color-coded timing lines, operator name detection
• UI consistency: Server Context pane always visible (placeholder when no metadata), Runtime Summary empty state, disabled Query Store button in file-mode toolbar
• Toolbar: Shortened button labels (Human Advice, Robot Advice, Copy Repro, Run Repro) to prevent overflow
• Wait Stats: Wider panel (2* column, MinWidth=280)

Test plan

• Open file-based .sqlplan — verify Server Context shows placeholder, Query Store button visible but disabled
• Expensive operators show multi-line format with CPU/elapsed percentages and node IDs
• Filter/lookup warnings render with bullet stats inside warning border (not escaping)
• Toolbar buttons fit without overflow on standard 1080p+ display
• All buttons visible in both Query Session and file-mode toolbars

🤖 Generated with Claude Code

Closes #48