[1.1 docs] Capture the 26 placeholder screenshots stripped for 1.0 ship

[malpern]

Seven published guides reference placeholder-*.png screenshots that were never captured. For the 1.0 public release these were stripped from the guide markdown (their ![...]() image lines removed) so they don't render as broken <img> icons on the website — the prose stands on its own. This issue preserves the exact capture list so the real screenshots can be added back in 1.1.

Each entry below records the guide, the intended filename, and the alt-text describing what to capture. When re-adding: capture against the signed 1.0 build, save to images/help/<name>.png, and restore the ![alt](.../<name>.png) reference at the spot the prose describes.
Total: 26 placeholder screenshots across 7 guides.

installation-wizard.md (4)

• placeholder-wizard-helper.png — Screenshot — Helper installation
• placeholder-wizard-accessibility.png — Screenshot — Accessibility permission
• placeholder-wizard-input-monitoring.png — Screenshot — Input Monitoring permission
• placeholder-wizard-complete.png — Screenshot — Setup complete

layers.md (2)

• placeholder-overlay-nav-layer.png — Screenshot — The overlay showing layer key hints
• placeholder-overlay-layer-transition.png — Screenshot — Overlay showing layer transition

qmk-import.md (3)

• placeholder-qmk-search.png — Screenshot — QMK keyboard search
• placeholder-layout-picker-custom.png — Screenshot — Layout picker with custom keyboards
• placeholder-qmk-import-options.png — Screenshot — QMK import options

remapping.md (4)

• placeholder-overlay-home-row-arrows.png — Screenshot — Home Row Arrows active in the overlay
• placeholder-pack-detail-arrows-picker.png — Screenshot — Home Row Arrows layout picker
• placeholder-pack-gallery-home-row-arrows.png — Screenshot — Home Row Arrows in the Pack Gallery
• placeholder-overlay-remapped-keys.png — Screenshot — The overlay highlighting remapped keys

script-execution.md (3)

• placeholder-settings-script-execution.png — Screenshot — Script Execution settings
• placeholder-script-confirmation.png — Screenshot — First-run script confirmation
• placeholder-script-execution-log.png — Screenshot — Script execution log

vallack-nav.md (7)

• placeholder-vallack-youtube.png — Screenshot — Ben Vallack's keyboard customization content
• placeholder-vallack-overlay-right.png — Screenshot — Right hand navigation keys in the overlay
• placeholder-vallack-overlay-left.png — Screenshot — Left hand switching keys in the overlay
• placeholder-vallack-modifier-comparison.png — Diagram — Standard vs Vallack modifier placement
• placeholder-vallack-pack-detail.png — Screenshot — Vallack pack detail with three collections
• placeholder-pack-vallack-install.png — Screenshot — Ben Vallack Nav in the Pack Gallery
• placeholder-vallack-workflow.png — Screenshot — Editing workflow with Vallack navigation

window-management.md (3)

• placeholder-overlay-window-snapping.png — Screenshot — Window Snapping layer in the overlay
• placeholder-accessibility-permission.png — Screenshot — Accessibility permission dialog
• placeholder-custom-rules-app-specific.png — Screenshot — App-specific rules in Custom Rules