feat(scenarios): add reusable raw-layout overrides

[bakasura980]

Greptile Summary

The PR adds reusable byte-level account override layouts for programs without an IDL and routes them through scenario materialization.

• Makes template IDLs optional and introduces raw encodings, account guards, and offset-based writes.
• Validates raw-layout collections before registration and prevents partial insertion of malformed collections.
• Adds raw-layout documentation and focused encoding, validation, and materialization tests.

Confidence Score: 4/5

The PR is not yet safe to merge because Studio cannot construct overrides from the newly exposed IDL-less raw-layout templates.

Raw-layout templates are returned with no IDL, but the coupled Studio editor still exits before account loading and exposes no raw-layout editing path, leaving the feature unusable through that supported client.

Files Needing Attention: crates/types/src/scenarios.rs and the coupled Studio scenario editor

Important Files Changed

Filename	Overview
crates/types/src/scenarios.rs	Adds the raw-layout wire and encoding model, but the optional IDL contract remains incompatible with Studio’s IDL-only editor flow.
crates/core/src/scenarios/registry.rs	Refactors collection loading and now validates required raw-layout metadata before mutating the registry.
crates/core/src/surfnet/svm.rs	Adds a raw-layout materialization path ahead of IDL lookup while preserving existing account metadata.
crates/core/src/scenarios/README.md	Documents IDL-less templates, raw offsets, encodings, account guards, and large-integer input requirements.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    T[Raw-layout template] --> V[Validate layout and properties]
    V --> R[Register template without IDL]
    R --> S[Schedule scenario override]
    S --> G[Check account size and magic]
    G --> E[Encode supplied values]
    E --> W[Write bytes at configured offsets]
    W --> A[Update local SVM account]

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_{Reviews (2): Last reviewed commit: "fix(scenarios): validate raw-layout temp..." | Re-trigger Greptile}

Context used:

• Knowledge Base — Runtime engine
• Knowledge Base — Shared data contracts