Toolbar: Tools menu, tool switcher, menu icons

[marcinz606]

Summary

• Tools menu on the canvas toolbar (icon-only, between Flip and Undo). It lists every canvas tool that has a toolbar row, grouped under its panel section: Geometry, Metering, Filtration, Dodge & Burn, Retouch. Each item shows the sidebar icon and the key. An item runs the tool's own shortcut action, so the tool's tab opens and a gated tool shows grayed out. Zone Placement is not in the menu, because it arms only from the zone strip.
• Tool switcher: when a tool is armed, its name on the tool row opens the same menu, so you go from Heal to Clone with no Done in between.
• The ⋯ menu has a Tools submenu. A saved toolbar row gets Tools once, before Undo. If the user removes it, it does not come back (toolbar_added_items).
• Overlays and Tools are icon-only. The Print and Overlays menu items now show icons. An item that is on shows its icon in the accent color, because the icon takes the place of the checkmark.
• An "Open Tools menu" action in the shortcut registry, with no default key.
• Fix: the Print menu grayed out Flat Scan until Flat output was on, but the peek works on any frame and the M key always worked.

Test plan

• make all
• Headless E2E on the real MainWindow: all 13 menu items arm their tools; Heal → Clone from the switcher arms Clone and turns the Heal sidebar button off; Flat Scan from the Print menu turns the peek on with Flat output off; the ⋯ Tools submenu is filled
• make run: arm each tool from the menu, check the tab reveal and Done/Esc

Open

• Heal and WB Picker use the same eye-dropper icon, and Transport Line and Card Edge both use grip-lines (these are the sidebar icons; the menu reuses them).