Improve discoverability and hover feedback for workspace navigation controls

[uzayer]

Problem

Workspace/navigation icon controls are difficult to identify at a glance. Users need a clear explanation on hover, plus a slightly more forgiving hover state/dismiss delay similar to Linear, so they can understand where Files, Knowledge, Git/commit surfaces, and related panel controls lead.

Investigation

• The current Cmd+B left panel is intentionally a file tree (src/features/layout/components/left-panel.tsx); Knowledge is a center tab and Git Graph is a right-panel surface.
• Existing navigation controls are spread across the titlebar, workspace sidebar, command palette, and right-panel section buttons.
• Many icon-only controls rely on native title attributes; Atlas has a tooltip z-index token but no shared delayed-tooltip primitive surfaced by this audit.
• The right panel’s controls include visible labels today, but the cross-panel controls do not form one consistent discoverability system.

Scope and acceptance criteria

• Audit all workspace/panel navigation controls, especially icon-only entry points, and assign clear names plus one-line purpose/tooltips.
• Use a shared accessible tooltip pattern with a deliberate show delay and short grace period after pointer leave, rather than inconsistent browser-native titles.
• Ensure the tooltip text describes the destination/action (for example “File Explorer”, “Knowledge Base”, “Git Graph / Commit History”), not merely the icon.
• Retain visible labels where present; do not replace them with tooltip-only UI.
• Keep tooltips positioned, layered, and timed consistently across titlebar, workspace sidebar, left/right panels, and compact/hover states.
• Verify keyboard focus also exposes equivalent accessible names and help.