Rework visor expansion

[pragmatrix]

There wasn't a clear separation between layout and animation. The non obvious solution was to avoid the expansion animation and layout the collapsed and expanded states only. After that, animation effects were caused implicitly by the transform updates which look the same.

[Copilot]

Pull request overview

This PR reworks the launcher “visor” behavior by removing the explicit expansion animation state and instead laying out only the collapsed vs expanded states, letting transform updates produce the visual transition implicitly. It also shifts “anchor” tracking to be driven by focus transitions rather than a dedicated expansion effect.

Changes:

• Removed visor expansion animation plumbing (UpdateLauncherExpansion effect, visor_expansion_animation, and associated presenter state).
• Introduced a per-launcher “focus anchor” mechanism and updates it on keyboard-focus transitions to choose the visor anchor when nothing is focused in that launcher.
• Refactored focus-transition handling to centralize effect application/forwarding and added a few clarifying comments / dictionary entries.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
desktop/src/projects/launcher_presenter.rs	Removes visor expansion animation state and uses a focus-anchor-based collapsed/expanded layout path.
desktop/src/desktop_system/layout_state.rs	Adds clarifying comments around child placement and size-change detection.
desktop/src/desktop_system/layout_effects.rs	Removes UpdateLauncherExpansion effect scheduling/handling and exposes instance_launcher to sibling modules.
desktop/src/desktop_system/focus_input.rs	Centralizes focus transition handling and updates launcher focus anchors on keyboard focus changes.
desktop/src/desktop_system/effects.rs	Removes the UpdateLauncherExpansion effect variant.
desktop/src/desktop_system.rs	Drops now-unneeded focus-resolution logic from apply_animations and documents deferred focus relayout tracking.
.harper-dictionary.txt	Adds project-specific terms to the spellcheck dictionary.
.github/copilot-instructions.md	Adds a guideline about keeping intra-function comments concise.