fix(frontend): keep the current branch when opening tasks from the header

[bilalabbad]

Why

Clicking the task-status button in the header while working on a non-default branch took you to the tasks page but silently reset the branch selector to main, so you lost your working branch just by checking on tasks.

The link built its branch query param from window.location, which nuqs updates one render after the branch context — so the href always lagged one branch switch behind (empty on the first switch), while its filters param carried the correct branch:

after picking platform-conflict:     href = /tasks?filters=[…"platform-conflict"]                ← no branch at all
after picking jfk1-update-edge-ips:  href = /tasks?branch=platform-conflict&filters=[…"jfk1-…"]  ← previous branch
after picking atl1-delete-upstream:  href = /tasks?branch=jfk1-update-edge-ips&filters=[…"atl1-…"]

What changed

• The header task-status link now keeps you on your current branch, and correctly drops the branch param when you are on the default branch.
• TaskStatus derives the param from currentBranch — which it already holds — instead of inheriting it from the ambient URL.
• Non-goal: constructPath still reads window.location during render, so the same staleness can affect any link rendered outside a useLocation subscriber. Left for a follow-up.

How to review

Single behavioural change in frontend/app/src/entities/tasks/ui/task-status.tsx. The is_default branchpoint exists because constructPath ignores a null value and needs exclude: true to remove a param.

How to test

cd frontend/app && pnpm vitest run src/entities/tasks/ui/task-status.test.tsx

Two new tests: the branch must come from the context (fails before this change), and the param must be absent on the default branch. Manually: switch to a non-default branch, click the task-status button, confirm the selector still shows your branch.

Impact & rollout

• Backward compatibility: none — URL shape unchanged, only correctly populated.
• Deployment notes: safe to deploy.

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Shadow auto-approve: would auto-approve. Bug fix: task-status link now uses the current branch from context instead of a stale URL value. The change is small, bounded, and covered by new tests.

Re-trigger cubic</sub>

[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Shadow auto-approve: would auto-approve. Focused frontend fix deriving the branch query param from current branch context instead of a stale URL value, with tests covering non-default and default branches. Bounded bug fix with no API, schema, or rollout impact.

Re-trigger cubic</sub>