v0.3.21: Code Plan detail page redesign

[SylonZero]

Summary

• Description card: long plan descriptions no longer push the page down. The header keeps title/badges/meta only; the description renders in its own card above the Design Spec, clamped to 5 lines with a Show more/less expander. The Progress / Target Assets / Assignees stats row now lands at the top of the viewport.
• Context tabs: Tasks, Assets & PRs, Impact Analysis, and Linked Work Items are now a tab group with counts in the labels and Tasks as the default tab — tasks are visible immediately on load, everything else is one click away. Empty Impact / Work Items tabs show explanatory empty states rather than disappearing.
• Add Task sits on the tab row, always reachable regardless of the active tab.
• Removed dead imports/styles left over from the old inline layout.

Tag v0.3.21 has been pushed with this changelog.

Test plan

• Verified live in a browser (Playwright, demo account): stats row at the top, tabs render as Tasks (10) | Assets & PRs (2) | Impact (0) | Work Items (0), Tasks content shows by default, and all tabs switch correctly.
• Verified the 5-line clamp + Show more/Show less with a temporarily lengthened multi-paragraph description (clamped 100px → expanded 280px, measured), and that short descriptions show no expander. Test data restored afterward.
• tsc --noEmit clean for the touched files (only the pre-existing documented errors elsewhere).

🤖 Generated with Claude Code