refactor(snaps-rpc-methods)!: Use messenger for restricted method implementations

[FrederikBolding]

Migrate the restricted method implementations to use the messenger where applicable.

https://consensyssoftware.atlassian.net/browse/WPC-995

---

Note

Medium Risk
Refactors multiple restricted RPC methods to use messenger-based controller actions instead of direct hook functions, which could subtly change runtime behavior and error handling across permissions, dialogs/notifications, and keyring-derived entropy. Broad test updates mitigate risk but the surface area is large and touches keyring/approval/state controllers.

Overview
Migrates restricted RPC methods to messenger-based actions. snap_dialog, snap_notify, wallet_snap, snap_manageState, and entropy/key derivation methods now accept a Messenger and call controller actions (e.g., approvals, snap interface, snap state, keyring access, rate limiting) instead of invoking dedicated hook functions.

Centralizes entropy-source access via new getMnemonic/getMnemonicSeed utilities (backed by KeyringController:withKeyring) and adds shared action type definitions in src/types.ts. Permission specification building is updated to create per-method restricted messengers using declared actionNames, and tests are rewritten accordingly (with new negative cases for invalid keyrings/entropy sources). Coverage thresholds are adjusted slightly, and snaps-simulation removes the obsolete get-mnemonic-seed and interface hook implementations/tests.

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[Mrtenz]

Maybe to match the UI messenger:

Suggested change

	actionNames: [
	'ApprovalController:addRequest',
	'SnapInterfaceController:createInterface',
	'SnapInterfaceController:getInterface',
	'SnapInterfaceController:setInterfaceDisplayed',
	],
	capabilities: {
	actions: [
	'ApprovalController:addRequest',
	'SnapInterfaceController:createInterface',
	'SnapInterfaceController:getInterface',
	'SnapInterfaceController:setInterfaceDisplayed',
	],
	}

[FrederikBolding]

createRestrictedMethodMessenger uses the actionNames naming, that's why I chose to name it like that for the specifications. Do you think it is cleaner to do: actionNames: capabilities.actions?

[Mrtenz]

No strong opinion, actionNames is fine with me.

[codecov]

Codecov Report

❌ Patch coverage is 99.07407% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.58%. Comparing base (dcb5bf9) to head (de25c13).

Files with missing lines	Patch %	Lines
...ackages/snaps-rpc-methods/src/restricted/notify.ts	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3968      +/-   ##
==========================================
+ Coverage   98.56%   98.58%   +0.02%     
==========================================
  Files         429      427       -2     
  Lines       12365    12399      +34     
  Branches     1944     1948       +4     
==========================================
+ Hits        12187    12223      +36     
+ Misses        178      176       -2     

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[FrederikBolding]

This mess is copied from the extension, suggestions for improvements welcome 🫠

[Mrtenz]

Wondering if we should add an action to the Snap controller for this, so we can fully remove the hooks?

[FrederikBolding]

The problem with these hooks is that they are client-specific. There is no platform-agnostic handler for getUnlockPromise that can also show the popup when needed on extension.

[Mrtenz]

Ah, good point. That may be something to implement in the wallet service for each client, but right now this is fine.

[Mrtenz]

Does this mean we create a messenger that has access to all the actions used by these methods? Should it be scoped to individual methods?

[FrederikBolding]

It is narrowed to the individual methods when building the specifications for the PermissionController here: https://github.com/MetaMask/snaps/pull/3968/files#diff-610e0a55f8b1fdc2b25489c558d3338b11c4c91e5dae790f891de1e97d6109bdR84-R88

[Mrtenz]

I don't love that we have to copy (and maintain) a bunch of types. We should definitely reconsider a messenger types package for each controller.

[FrederikBolding]

Me neither.

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