Route bindings (ghtmx)

The five verb attributes accept a handler symbol (hx-post={ handlers.CreateUser }, zero-parameter routes, path folded statically) or a generated constructor (hx-get={ ghtmxgen.GetUser(id) }, parameters percent-encoded), resolved at build time against routes discovered from Go source (FR-020/FR-021). Registrations the discoverer cannot resolve use the escape hatch: //ghtmx:route GET /admin/users/{id} handlers.Show. Other hx-* attributes are validated against the pinned htmx version's surface (internal/htmxsurface).

Verified by: examples/hx-bindings, examples/crud, internal/analyzer, internal/routes, conformance.