Adds a GitHub-hosted macos-15 (Apple Silicon) workflow for pushes and PRs
into the macos branch: build with Homebrew GCC, once with PORT_ADDR_STRICT
off and once on, then run the ROM-free address-model self-test.
- main.c: new --selftest flag, handled right after portAddrInit() and
before crashInit/config/ROM/SDL. Exits 0 if the self-test passed, 1 if
not. Listed in --help.
- port_addr.c/.h: portAddrSelfTest() now returns its result and
portAddrSelfTestPassed() exposes it; no change to normal runs.
- macos.yml: contents: read only, no secrets, no ROM, persist-credentials
off, so it is safe for fork PRs. The strict entry also requires the
GE_ADDRSTRICT_SELFTEST report, proving the validator is live.
- docs: building.md CI note; plan M4 row no longer lists macOS CI as
outstanding (ROM sweeps stay with the self-hosted job in #131).
Dan Turner
7b08a04f54