Add accessible tooltips to icon-only actions

Problem

Many UI actions are represented by icons alone. Even when an icon has an accessible name, its meaning is not always obvious to sighted users, especially for less familiar actions and controls that appear only in certain page states.

Desired behavior

Icon-only actions should explain themselves consistently on pointer hover and keyboard focus without adding persistent visual noise to the dense work-tool layout.

Acceptance criteria

• Add a shared tooltip treatment for icon-only buttons and links rather than implementing page-specific variants.
• Show a concise action label on pointer hover and keyboard focus.
• Give every icon-only interactive control a matching accessible name via aria-label or equivalent semantics.
• Keep tooltip text action-oriented and consistent with any nearby menu or button wording.
• Ensure tooltips do not block the target, clip inside cards/overflow containers, or extend beyond narrow viewports.
• Support light and dark modes and respect reduced-motion preferences.
• Do not add redundant tooltips to controls whose visible text already explains the action.
• Audit the main project, issue, sprint, context, attachment, settings, and navigation surfaces.
• Add component/render tests for mouse, keyboard-focus, accessible-name, and dark-mode markup.