bug: CreateWorkspace resolves paths against CWD instead of git root

[nextlevelshit]

Bug

CreateWorkspace resolves .wave/workspaces/ relative to the process CWD instead of the git root. When tests run from internal/pipeline/, workspaces get created at internal/pipeline/.wave/workspaces/ instead of .wave/workspaces/.

Evidence

Found ~90+ misplaced .wave/workspaces/ directories across three categories:

1. Source packages — internal/pipeline/.wave/workspaces/, internal/webui/.wave/workspaces/, tests/integration/.wave/workspaces/
2. Nested inside worktree workspaces — ~30 pipeline runs where sub-workspaces were created inside worktree CWD subdirectories
3. Claude Code agent worktrees — .claude/worktrees/agent-*/internal/pipeline/.wave/workspaces/

Each misplaced workspace is a full project worktree (git worktree with .git pointer), wasting disk and polluting the tree.

Root Cause

CreateWorkspace computes the workspace base path from os.Getwd() (or step CWD) rather than always resolving to the git root.

Fix (two parts)

1. Code: CreateWorkspace must resolve workspace paths against git root, never CWD
2. .gitignore: Add **/.wave/workspaces/ wildcard to catch any future strays

Verification

Check if the fix already landed — memory notes git init -q in mount/basic workspaces as a prior fix for path resolution. If git root resolution is already wired up, this may just need the .gitignore wildcard.

[nextlevelshit]

Fix already landed on main:

• resolveGitRoot() helper at internal/workspace/workspace.go:45
• NewWorkspaceManager resolves relative baseDir against git root at internal/workspace/workspace.go:58
• .gitignore has the **/.wave/workspaces/ wildcard safety net
• All Phase 1 and Phase 2 tasks marked complete in specs/1124-workspace-git-root/tasks.md

If stray workspaces reappear, please open a fresh bug with the pipeline run ID that created them.