feat: consolidate worktree-branch-delete into worktree-branch -d/-D

[avihut]

Summary

• Absorbs the standalone git-worktree-branch-delete command into git-worktree-branch -d/-D, mirroring how git branch -d/-D works
• Follows the same pattern established in feat: add daft verb aliases and consolidate checkout-branch into checkout -b #250 (consolidating checkout-branch into checkout -b)
• daft remove now injects -d before clap parsing (same as daft start injects -b)
• The old git-worktree-branch-delete is kept as a deprecated backward-compat shim with a stderr warning

Changes

New command: git worktree-branch -d/-D

• -d (safe delete): checks merge status, uncommitted changes, remote sync
• -D (force delete): bypasses safety checks (except default branch protection)
• Error without -d/-D with usage hint

Routing updates

• daft remove → worktree_branch::run_remove() (injects -d)
• gwtbd shortcut → git-worktree-branch -d
• Shell wrappers updated for bash/zsh/fish

Backward compatibility

• git worktree-branch-delete still works, prints deprecation warning
• All existing integration tests continue to pass unchanged

Test plan

• mise run fmt passes
• mise run clippy passes (zero warnings)
• mise run test:unit passes (366 tests)
• mise run man:verify passes
• mise run docs:cli:verify passes
• mise run test:integration — new tests for -d, -D, no-flag error, and deprecation warning
• Manual test: git worktree-branch -d <branch> safe delete
• Manual test: git worktree-branch -D <branch> force delete
• Manual test: daft remove <branch> still works
• Manual test: git-worktree-branch-delete <branch> shows deprecation warning

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