feat: resolve(uri) / uri_of(entity) with round-trip guarantees

[rahlk]

resolve(uri) -> Symbol and uri_of(entity) -> str on every analysis facade, implementing the URI RFC over the canonical adapters.

Acceptance

• Round-trip property tests per language: resolve(uri_of(x)) == x for every symbol in the bundled sample apps.
• Collision test: no two distinct symbols in a sample app share a URI.
• Unresolvable URIs raise a typed error (not None) carrying a nearest-match hint.

Part of #194. Branch: feat/issue-<n>.