Task 1.2: SDP Installer Test Suite source-swapping capability.
Adds swap_source.sh (park/restore or fresh-clone via p4-sdp_*/test-install_sdp_* remote specs) and bootstrap_test_machine.sh (self-contained, curl-bootstrappable machine-join script, SDP Bash Coding Standard style with documented deviations, ShellCheck-clean). Fixes dev_env.sh's hardcoded P4USER/P4PORT, and init_root_dirs_for_local_installs.sh's stale r25.1 P4D default and a real bin.aarch64 URL bug (404; should be bin.linux26aarch64). Restructures InstallSDP-TestServerSetup.md around the new bootstrap script and adds a "Qualifying a New Platform" section.
Agent: Claude Code, Model: Claude Sonnet 5 (claude-sonnet-5), operating as bot_Claude_Anthropic.