HostWorkingDir and position-aware default scope

[UltraBob]

Enable HostWorkingDir: true on all commands and implement position-aware default scope. Ordering matters: fix COMMANDS_DIR before enabling HostWorkingDir.

Work items (order-sensitive)

1. Fix COMMANDS_DIR in checks and checks-full first — currently ./.ddev/commands/web/<tool>, fails from non-root dirs
2. Re-anchor all default scopes to $DDEV_APPROOT and dcq-reports/ to project root
3. Add HostWorkingDir: true to every command
4. Position-aware defaults: at project root with no args → scan custom dirs; elsewhere → scan cwd
5. Gate default path injection on no positional paths AND not stdin mode
6. Port host-working-dir.bats; add stdin-gating tests

Acceptance criteria

• COMMANDS_DIR fixed before HostWorkingDir is enabled
• All default scopes anchored to $DDEV_APPROOT
• HostWorkingDir: true on every command
• Position-aware defaults: root → custom dirs, non-root → cwd
• --stdin-path does not trigger default scope injection
• Tests pass

Blocked by: ADRs for position-aware defaults and working directory (PRs pending)