Replaced project instruction expanders with tabs #242

Commit e4cbc50 replaces the nested Project Instructions preview and version-history expanders with explicit tabs and a directly visible revision browser.

Editing now uses Write and Preview tabs with a useful empty preview. Reading uses Instructions and Version history tabs; history shows a revision list on the left and the selected rendered revision on the right, with a clear empty state and responsive single-column behavior. A focused server-rendered UI contract test passes. The full suite reached 87 passing tests but one unrelated TaskPatch MCP test failed against concurrent uncommitted MCP changes, which were preserved and excluded from this commit.