feat(scenarios): add reusable raw-layout overrides

[bakasura980]

Greptile Summary

The PR introduces optional IDL-free templates backed by guarded raw byte layouts, exact integer encodings, strided writes, and a new materialization path in the SVM.

• Adds raw-layout metadata and integer/pubkey/slot encodings to shared scenario types.
• Loads no-IDL override collections and applies them directly to existing account bytes.
• Updates IDL-dependent tests and documentation for optional template IDLs.

Confidence Score: 4/5

The PR should not merge until the coupled Studio client can select and edit templates whose IDL is intentionally absent.

Raw-layout templates are emitted with idl: null, while Studio’s current action-selection path rejects exactly that shape; loader validation is also deferred until materialization.

Files Needing Attention: crates/types/src/scenarios.rs, crates/core/src/scenarios/registry.rs

Important Files Changed

Filename	Overview
crates/types/src/scenarios.rs	Adds the raw-layout contract and encoders, but making template IDLs optional is not yet supported by the coupled Studio consumer.
crates/core/src/surfnet/svm.rs	Adds guarded raw-byte materialization before IDL lookup and preserves account-level metadata.
crates/core/src/scenarios/registry.rs	Adds no-IDL collection loading, but accepts structurally incomplete raw-layout templates without early validation.
crates/core/src/scenarios/README.md	Documents raw-layout YAML, guarded writes, little-endian encoding, and large-integer string handling.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Scenario[Scheduled override] --> Resolve[Resolve account]
  Resolve --> Layout{Template has raw layout?}
  Layout -->|Yes| Guard[Check size and magic]
  Guard --> Encode[Encode supplied values]
  Encode --> Write[Write offsets and strides]
  Write --> State[Update local account]
  Layout -->|No| IDL[Existing IDL materialization]
  IDL --> State

Loading

Prompt To Fix All With AI

### Issue 1
crates/types/src/scenarios.rs:396-400
**Optional IDL breaks Studio**

When a raw-layout template is returned with `idl: null`, Studio's action-selection handler rejects it as missing an IDL and returns before fetching the account or constructing the override. This makes raw-layout templates unusable in the coupled [scenario editor](https://github.com/limechain/surfpool-web-ui/blob/HEAD/apps/studio/src/components/svm/scenario-editor.tsx#L524-L533), despite exposing them through the same template contract.

### Issue 2
crates/core/src/scenarios/registry.rs:195-198
**Raw-layout invariants remain unvalidated**

`load_raw_layout_overrides` accepts collections without `raw_layout` and writable properties without both `offset` and `encoding`. These invalid templates are inserted successfully and fail only during scheduled materialization, leaving the account unchanged after emitting a warning; validate the required combinations while loading the collection.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(scenarios): add reusable raw-layout..." | Re-trigger Greptile}

Greptile also left 2 inline comments on this PR.

Context used:

• Knowledge Base — Scenario execution
• Knowledge Base — Shared data contracts

[greptile-apps]

Optional IDL breaks Studio

When a raw-layout template is returned with idl: null, Studio's action-selection handler rejects it as missing an IDL and returns before fetching the account or constructing the override. This makes raw-layout templates unusable in the coupled scenario editor, despite exposing them through the same template contract.

Knowledge Base Used: Shared data contracts

Prompt To Fix With AI

This is a comment left during a code review.
Path: crates/types/src/scenarios.rs
Line: 396-400

Comment:
**Optional IDL breaks Studio**

When a raw-layout template is returned with `idl: null`, Studio's action-selection handler rejects it as missing an IDL and returns before fetching the account or constructing the override. This makes raw-layout templates unusable in the coupled [scenario editor](https://github.com/limechain/surfpool-web-ui/blob/HEAD/apps/studio/src/components/svm/scenario-editor.tsx#L524-L533), despite exposing them through the same template contract.

**Knowledge Base Used:** [Shared data contracts](https://app.greptile.com/limechain/-/custom-context/knowledge-base/limechain/surfpool/-/docs/shared-data-contracts.md)

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

[greptile-apps]

Raw-layout invariants remain unvalidated

load_raw_layout_overrides accepts collections without raw_layout and writable properties without both offset and encoding. These invalid templates are inserted successfully and fail only during scheduled materialization, leaving the account unchanged after emitting a warning; validate the required combinations while loading the collection.

Knowledge Base Used: Scenario execution

Prompt To Fix With AI

This is a comment left during a code review.
Path: crates/core/src/scenarios/registry.rs
Line: 195-198

Comment:
**Raw-layout invariants remain unvalidated**

`load_raw_layout_overrides` accepts collections without `raw_layout` and writable properties without both `offset` and `encoding`. These invalid templates are inserted successfully and fail only during scheduled materialization, leaving the account unchanged after emitting a warning; validate the required combinations while loading the collection.

**Knowledge Base Used:** [Scenario execution](https://app.greptile.com/limechain/-/custom-context/knowledge-base/limechain/surfpool/-/docs/scenario-execution.md)

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.