fix: preserve viewer focus and tab-colored task accents

[markwylde]

Summary

• Keeps viewer panels focused when restoring focus after edit project/tab windows close, instead of activating an unrelated terminal.
• Passes tab/project color into file and folder viewers so task progress accents follow the active tab color.
• Removes the old task gradient/card status accent styling now replaced by the tab color.

Verification

• npm run smoke

Commits

• fix(workspace): preserve active viewer focus
• fix(viewer): use tab color for task accents