Carve-outs and corpus exclusions (FR-004)

The two semantic carve-outs from the baseline, each with its replacement construct — itemized case-by-case in CONFORMANCE.md:

1. hx-* verb attributes are typed bindings. A string URL is GHTMX-E0602, an arbitrary expression GHTMX-E0601; the replacements are the handler-symbol and constructor binding forms above.
2. URL escaping at binding sites is engine-determined. An explicit ghtmx.URL/SafeURL call at a binding site is GHTMX-E0603; the replacement is the ghtmx.SafeURL-returning generated constructor. (ghtmx.URL for href/action and friends is inherited unchanged.)

Non-carve-out corpus exclusions, each documented with its reason and replacement in CONFORMANCE.md's exclusion list: the baseline's runtime-fragment API (its test-fragment golden dir) is removed in favor of fragment declarations, and the baseline's Prettier-dependent formatter and HTML-diff behavior is replaced with verbatim pass-through and structural comparison.