fix: node should always cache contract WASM on GET, regardless of return_contract_code

[sanity]

Problem

When a client sends a GET with return_contract_code: false, the node does not cache the contract WASM locally. This means:

• SUBSCRIBE fails with "contract WASM/parameters not cached locally"
• The node cannot validate incoming updates for the contract
• The node cannot host the contract for other peers

Expected Behavior

return_contract_code should only control whether the WASM bytes are included in the response to the client (bandwidth optimization). The node should always fetch and cache the WASM internally so it can:

• Accept and process SUBSCRIBE requests
• Validate contract state updates
• Host the contract state for the network

Current Workaround

Delta sets return_contract_code: true on all GET requests, but this wastes bandwidth sending the WASM to the client (which already has it embedded).

Context

Found while debugging Delta subscription failures. The node log showed:

Cannot cache or subscribe to contract - no contract code in GET response
Rejecting SUBSCRIBE: contract WASM not cached locally

[AI-assisted - Claude]

[github-actions]

🤖 Auto-labeled

Applied labels:

• T-bug (95% confidence)
• P-high (90% confidence)
• E-medium (75% confidence)
• A-contracts (95% confidence)

Reasoning: This is a functional regression where the node fails to cache contract WASM when return_contract_code=false, causing SUBSCRIBE failures, inability to validate updates, and inability to host contracts — classifies as a bug. It likely impacts many users and core functionality (subscriptions/hosting), so priority is high. Fixing requires changing caching behavior and internal fetch logic (moderate complexity -> E-medium). The problem is primarily in the contract runtime/contract handling code (A-contracts) and also affects network behaviors (subscriptions/hosting) so A-networking is relevant.

Previous labels: none

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