20260610_000000_readonly_mutable_engine.md

bump	minor

Added

• AccessMode { Mutable, ReadOnly } setting on ParseConfiguration (with_access_mode / access_mode), defaulting to Mutable so existing callers are unaffected.
• LinkNetwork::freeze / as_read_only yielding a ReadOnlyNetwork view that exposes only &self operations (query, project, reconstruct, verify, serialize); mutators are unreachable at compile time because the view never hands out &mut LinkNetwork.
• LinkNetwork::parse_engine, returning an EngineNetwork handle that honours the configured access mode: read-only parsing returns the frozen form and EngineNetwork::as_mutable rejects mutation with a ReadOnlyViolation diagnostic.
• Snapshot interop: NetworkSnapshot::as_read_only / from_read_only reuse the snapshot's Arc<LinkNetwork>, so the frozen form composes with snapshot versioning instead of duplicating it.