fix(session-creator): refine worktree source modal

[Harry19081]

Problem

The worktree source dialog used custom modal actions and compact input treatments that did not match the work-item picker. Its Smart and Name entry paths duplicated the clearer Branch/GitHub choices, branch ordering could bury the current/default branches, and checked-out worktrees used a different icon from Branch Spotlight.

Solution

Use the standard large Modal action props with localized Cancel/Create labels, keep only Branch and GitHub tabs with Branch selected by default, and align search, refresh, tabs, rows, spacing, and icons with the existing design-system patterns. Promote the current branch and conventional default branches to the top without duplicating them, preserve worktree metadata, and localize the dialog states across all supported session locales.

Potential risks

The removed Smart and Name tabs are no longer available by design; users choose a branch/ref or GitHub item instead. Default-branch promotion recognizes the same conventional names as Branch Spotlight (main, master, develop, dev), so repositories with a nonstandard default still rely on current/recent ordering. No API, persistence, schema, or dependency changes are included. Rollback is a direct revert of commit 6c506a4.

Verification

• npx vitest run src/features/SessionCreator/components/WorktreeSourceModal.test.ts src/features/SessionCreator/components/__tests__/worktreeBranchSource.test.ts src/features/SessionCreator/components/__tests__/worktreeSmartInput.test.ts — 57 tests passed.
• Scoped ESLint over the seven changed TypeScript/TSX files — passed.
• Prettier check over changed source and locale files — passed.
• npm run typecheck — passed.
• Commit hooks: lint-staged, scoped TypeScript, and circular-dependency checks — passed.
• Worktree-source locale key parity checked across 13 locales — passed.
• Staged diff checked for whitespace errors, personal paths, private keys, debug logs, and obvious credential fields — clean.

No final-state screenshot was attached because desktop Computer Use is explicit opt-in in this workspace and was not requested; component-level assertions cover modal props, tab order/treatment, GitHub SVG usage, and compact row sizing.

Audit

The configured frontend-ui-audit skill was unavailable at both documented locations. A manual design-system review confirmed use of standard Modal, SearchInput, Button, ListPanel, GitHub asset, and Branch Spotlight patterns.