Sidebar navigation: Replace Dashicons icon font with @wordpress/icons SVGs in the sidebar navigation

[lucasmdo]

Problem / Current Behavior

The admin sidebar menu draws its top-level icons using the Dashicons icon font. This is the same legacy approach described in the parent ticket #65089, seen here specifically in the left-hand admin navigation.

Proposed Enhancement

Replace the Dashicons font icons on Core's default top-level admin menu items with SVG icons from the @wordpress/icons library — the same set already used by the editors. The icons keep their current look, position, and labels; only the underlying technique changes.

Worth noting: Core already supports SVG icons for admin menu items (via the menu icon API) and already recolors them to match the active color scheme (#25147), so the rendering path for SVG menu icons exists today. This ticket applies that direction to Core's own default items.

In scope — Core's own default top-level menu icons (Dashboard, Posts, Media, Pages, Comments, Appearance, Plugins, Users, Tools, Settings) and the "Collapse menu" button icon at the bottom of the menu (#50423).

Out of scope:

• Menu icons added by plugins or themes → see Backward Compatibility.
• Restructuring or grouping the navigation itself → this ticket only changes the icon technique.
• The admin bar icons → handled by the sibling Toolbar ticket in this series (#65386).

Rationale

• Consistency: brings the admin menu in line with the icon set already used by the editors, and supports the broader WP 7.0 admin visual reskin (#64308).
• Performance: removes a major reason the icon font is loaded on every admin page, and lets new icons be added without growing a single large font file.

Note: per feedback on #65089, screen-reader benefits here are modest compared to today's approach. The real gains are consistency, performance, and reliability.

Backward Compatibility

• Low-risk and additive. Only Core's own default icons change; their position, labels, and behavior stay the same.
• The public menu icon API is untouched: plugins and themes can still pass a Dashicons class or their own SVG when registering menu items, and the Dashicons stylesheet must stay available for them.
• No change to how the menu is built, to its hooks, or to keyboard navigation.

Related Tickets / References

• #65089 — parent / umbrella: replace Dashicons with @wordpress/icons across wp-admin
• #64308 — broader WP 7.0 admin visual reskin (the "Admin Frame": sidebar + toolbar)
• #25147 — existing SVG support and recoloring for admin menu icons (prior art)
• #50423 — the "Collapse menu" button icon (in scope here)
• #50539 — exploration of an icon-less admin menu (distinct: this ticket keeps the icons)
• #47012 — proposal to simplify admin navigation (distinct: structure, not icon technique)
• ​@wordpress/icons package

[lucasmdo]

Updating the title to be clearer.

[lucasmdo]

#65089: parent / umbrella: replace Dashicons with @wordpress/icons across wp-admin