chore: add backlog TASK-70 — selector tool with marquee multi-select (done)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backlog/tasks/task-70 - Default-selector-tool-with-marquee-multi-select.md

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+---
+id: TASK-70
+title: Default selector tool with marquee multi-select
+status: Done
+assignee: []
+created_date: '2026-02-28 00:36'
+updated_date: '2026-02-28 00:36'
+labels:
+  - canvas
+  - UX
+  - selection
+dependencies: []
+references:
+  - lib/folk-shape.ts
+  - website/canvas.html
+priority: high
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Replace single-click-to-pan with selector as the default canvas tool. Left-click-drag on background draws a blue marquee rectangle to select multiple shapes. Shift/Ctrl+click toggles additive selection. Panning moves to Space+drag, middle-click, or wheel/trackpad. Delete/Backspace removes all selected shapes. folk-shape highlighted state shows blue selection outline.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [x] #1 Click canvas background → nothing selected, no pan
+- [x] #2 Click-drag on background → blue marquee rectangle appears
+- [x] #3 Release marquee → all overlapping shapes highlighted with blue outline
+- [x] #4 Shift+click a shape → adds/removes from selection
+- [x] #5 Click a single shape → only that shape selected
+- [x] #6 Hold Space + drag → pans the canvas (cursor shows grab)
+- [x] #7 Middle-click + drag → pans the canvas
+- [x] #8 Two-finger scroll → still pans (unchanged)
+- [x] #9 Ctrl+scroll → still zooms (unchanged)
+- [x] #10 Delete/Backspace → removes all selected shapes
+- [x] #11 Click toolbar tool → crosshair cursor → click to place (unchanged)
+- [x] #12 bunx tsc --noEmit passes
+<!-- AC:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Implemented default selector tool with marquee multi-select. Changed folk-shape.ts highlighted CSS to show blue outline. Rewrote canvas.html pointer handlers: left-click-drag draws marquee selection rectangle, Space+drag and middle-click for panning, Shift/Ctrl+click for additive selection, Delete/Backspace to remove selected shapes. Commit 1d8fc2b on dev, merged to main.
+<!-- SECTION:FINAL_SUMMARY:END -->