Enforce the no-CAS-management boundary and reachability proof

[flyingrobots]

Parent: #734
Blocked by: #735 through #741

Outcome

CI mechanically prevents WARP-owned CAS/cache management from returning.

Scope

• AST/import boundary forbidding direct raw object writes, RootSet coordination, cache indexes, LRU/page-cache implementations, and plumbing reflection in production WARP code.
• Allowlisted composition root imports of the public git-cas API.
• Real-repository reachability test for live, replaced, expired, and pinned assets.
• Constrained-memory integration test for a blessed bounded reading.
• Public API/consumer tests proving no removed storage substrate leaks back into root.

Proof

• Mutation tests demonstrate the gate fails on forbidden examples.
• Live materializations are absent from immediate-prune output.
• Released/expired cache values become eligible for collection.
• Test output and source citations are recorded as goalpost evidence.

[coderabbitai]

🔗 Related PRs

#79 - feat: auto-materialize in createPatch when removes need state [merged]
#574 - Gate 1: enforce first-use optics honesty [merged]
#708 - Fix live materialization state-cache hits [merged]
#726 - Move graph exports behind v19 public API boundary [merged]
#728 - Add openWarp timeline facade [merged]

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[flyingrobots]

Proof-gate addendum\n\nThe constrained-memory/reachability gate must also include a warm-reopen scenario: build a materialization, close local Runtime resources, reopen, repeat the same bounded Observer, and prove through counters that no already-covered patches are reduced and no unrelated pages are opened. This is the regression gate for the reported every-run cold materialization behavior.