fix: use own-property resource lookups

[han4wluc]

Resource registries and section maps are read with plain property access, so an ID equal to an Object.prototype member resolves to the inherited value: a missing section toString returns a function, and a missing colour constructor produces a misleading hex-colour error.

Reproduce: look up a section or resource whose ID is toString or constructor when no such entry exists (regression tests).

Fix: registries and section maps are read with own-property lookups; valid own keys with those names still work.

Tests: the new regressions; the full suite (2,166 tests) and lint pass.