feat(api): implement stream-conditional colour API and runtime policy

[synesissoftware]

Introduce a compiled runtime library component to complement the existing header-only SGR macros. The object-like colour macros remain unbound and require no linking; the compiled component adds stream-conditional colour sequences, environmental policy parsing, Windows console virtual-terminal gating, and runtime ABI version inspection.

Key changes:

• add runtime version functions woad_version() and woad_version_string() in src/api.c to provide an ABI probe;
• implement stream-conditional colour selection and stream inspection for FILE*, file descriptor, and Windows console handles;
• provide function-like conditional macros (WOAD_SEQ_FOR, WOAD_FG_FOR, WOAD_RESET_FOR, and colour-named variants) with type dispatch via _Generic in C11+ and overloading in C++;
• evaluate environmental colour policy honouring WOAD_COLOUR / WOAD_COLOR, NO_COLOR, CLICOLOR_FORCE, CLICOLOR, and TERM=dumb;
• support WOAD_SET_CONSOLE_MODE to withhold console modification while falling back to querying existing virtual-terminal capability;
• gate Windows virtual-terminal processing via RtlGetVersion() and SetConsoleMode(), elected once per module/process via atomic CAS;
• transition woad to a compiled library target in CMakeLists.txt and update woad.pc.in, while retaining unbound header-only SGR macros;
• add section-3 manual page template man/woad.3.in, example colour_for.c, and unit tests in test.unit.gating.c and test.unit.version.c;
• support --build-shared-libs in prepare_cmake.sh and unify options passed across MinGW and default CMake invocations;
• smoke-test colour policy and precedence in CI across all matrix cells, and advance version to 0.0.1-beta1;