fix(taskctl): create pipeline worktrees under .worktrees/ inside project (#286)

[randomm]

Fixes #286

Changes

• worktree/index.ts: add optional rootPath to CreateInput — when provided, worktrees are created there instead of ~/.local/share/opencode/worktree//
• pulse.ts spawnDeveloper: pass rootPath = Instance.directory + '/.worktrees' so pipeline tasks get worktrees inside the project
• pulse.test.ts: two new tests covering rootPath behaviour

Why

Pipeline worktrees were created in ~/.local/share/opencode/worktree/ causing:

• Permission dialogs when @ops accessed them
• Hard to inspect task work
• Inconsistency with manual @ops worktrees (which live in .worktrees/)
• Main project landing in detached HEAD state

.worktrees/ is already in .gitignore. Backward compatible — callers without rootPath use the old default.