glia: PR-2 durable collection summary bits and ownership seam transforms

[lthibault]

Extend the persistent-collection work with compositional value-domain summaries.

Scope:

• Maintain per-node contains-executable and durable-certified summaries for List, Vector, Map, and Set.
• Make durability certification construction-time and O(1) to check; false positives must be impossible.
• Use the summaries to keep ownership transforms out of pure durable data and to optimize local mixed-value transforms.
• Define content hashing only for certified durable values; local pointer identity must never enter durable identity.
• Add seam-transform and conformance tests for structural sharing, pure-data fast paths, and A-contaminated collections.

Depends on the definition-ownership substrate and refines #199 and #200.

Out of scope: a distinct durable collection type is a PR-2 decision, not a prerequisite.