feat: remove all MYX protocol from core

[abretonc7s]

Explanation

@metamask/perps-controller shipped a full MYX protocol implementation alongside HyperLiquid and
Lighter. MYX is being dropped as a venue, and keeping it cost real weight: an optional
@myx-trade/sdk dependency, a dynamic-import + webpackIgnore workaround plus three
!dist/*MYX* files exclusions so extension bundles could skip the provider, and 'myx'
branches threaded through the controller, the provider router, and the provider-type unions.

This PR removes MYX from the package. It deletes MYXProvider, MYXClientService,
MYXWalletService, the MYX adapter, and the MYX config and type modules along with their test
suites; drops the @myx-trade/sdk dependency and the packaging exclusions it required; and
de-wires the controller — #isMYXProviderEnabled, the dynamic-import registration path,
registerMYXProvider, handleMYXImportError, resolveMyxAuthConfig, and the 'myx' routing and
cache-key branches all go. Net: ~8,700 lines removed across 42 files.

Notable API effects, all breaking for consumers that used MYX:

• PerpsProviderType is now 'hyperliquid' | 'lighter'. switchProvider('myx') returns
  { success: false, error: 'Provider myx not available' }. A 'myx' value restored from
  persisted state falls back to 'hyperliquid' and rewrites the persisted value, so existing
  MYX users self-heal on next launch rather than getting a broken perps tab.
• The MYXCredentials type and providerCredentials.myx option are gone.
• All MYX_* constants, getMYXChainId / getMYXHttpEndpoint, the fromMYX* / toMYX*
  converters, and the MYX-only USDT_BNB_TESTNET / USDT_BNB_MAINNET collateral addresses are no
  longer exported.
• PROVIDER_CONFIG.MYX_TESTNET_ONLY is removed; buildProviderCacheKey no longer special-cases
  'myx'.
• The perpsMyxProviderEnabled remote flag and MM_PERPS_MYX_PROVIDER_ENABLED env override are
  no longer read, so clients can retire both.

Two changes may not be obvious:

• packages/authenticated-user-storage is touched deliberately. PerpsWatchlistMarkets.myx
  is a server-persisted preference schema, not protocol code, and blobs already stored remotely
  contain a myx key. Deleting the required field would have failed validation on that existing
  data. It is instead made optional() and @deprecated: nothing writes it any more, stored
  blobs still validate, and perps-controller is left with zero MYX references.
• The files field is now plain ["dist/"]. With the MYX exclusions gone, everything emitted
  into dist/ publishes — so a stale dist/ from a previous build would ship MYX artifacts. The
  validation below uses yarn build:clean (which wipes packages/*/dist first) and asserts the
  emitted tree contains no MYX file at all.

HyperLiquid and Lighter behavior is unchanged. Where MYX served only as "a second provider" in
multi-provider aggregation, routing, and cache tests, those cases were repointed at Lighter rather
than deleted, so multi-provider coverage is preserved.

Validation

• yarn workspace @metamask/perps-controller run test — 79 suites, 3399 passed, 0 failures,
  coverage thresholds met (89.4% lines vs 80% required, 81.54% branches vs 69%, 85.58% functions
  vs 78%).
• yarn workspace @metamask/authenticated-user-storage run jest — 44 passed, 0 failures.
• yarn build:clean (root ts-bridge) — exit 0, "Project built successfully"; the emitted
  packages/perps-controller/dist contains no MYX file, and dist/index.d.cts / dist/index.cjs
  export no MYX symbol.
• ESLint over changed files — 0 errors. Prettier — clean. yarn changelog:validate — passes.
• An end-to-end proof recipe asserts the removal (no MYX in src//tests/, none in the manifest,
  none in the built dist/) and then reads live HyperLiquid testnet positions, orders, and
  account state through the de-wired controller to show the removal caused no regression. The
  assertions were confirmed to fail against the pre-change tree, so a revert of this diff breaks
  the recipe.

References

• https://consensyssoftware.atlassian.net/browse/TAT-3892

Client follow-ups needed before/alongside adoption:

• Mobile and extension must drop any providerCredentials.myx, activeProvider: 'myx', or
  providerId: 'myx' usage and remove MYX from provider pickers.
• The perpsMyxProviderEnabled remote feature flag can be retired once clients are updated.
• A future AUS schema migration can drop the deprecated myx watchlist key entirely once no
  stored blob relies on it.

Checklist

• I've updated the test suite for new or updated code as appropriate
  • MYX-only suites deleted; shared multi-provider tests repointed at Lighter so aggregation,
    routing, and cache coverage is preserved.
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
  • JSDoc examples that used 'myx' as a sample provider now use 'lighter'; comments in the
    Lighter provider, wallet service, and adapter that referenced MYX as their template were
    rewritten to stand alone.
• I've communicated my changes to consumers by updating changelogs for packages I've changed
  • perps-controller (Removed, **BREAKING:**) and authenticated-user-storage (Changed).
• I've introduced breaking changes in this PR and have prepared draft pull requests for
  clients and consumer packages to resolve them
  • Breaking changes are introduced and documented above, but the client draft PRs are not yet
    open. They are listed under References and should land before this is adopted.

Screenshots/Recordings

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Note

Medium Risk
Breaking public API and large deletion in perps routing/initialization; mitigated by persisted-provider fallback and optional deprecated AUS myx key for stored preferences.

Overview
Removes the MYX perpetuals venue from @metamask/perps-controller: provider, client/wallet services, adapters, config/types, SDK optional dependency, dynamic registration, and all public MYX_* exports. PerpsProviderType is now 'hyperliquid' | 'lighter'; MYXCredentials / providerCredentials.myx, the perpsMyxProviderEnabled flag, and related env overrides are gone.

#assignActiveProvider no longer throws on an unknown persisted activeProvider—it falls back to HyperLiquid and rewrites state so older 'myx' selections self-heal. AUS watchlist writes no longer seed a myx entry; multi-provider tests that used MYX were repointed to Lighter.

In authenticated-user-storage, PerpsWatchlistMarkets.myx is @deprecated and optional in types and validators so existing server preference blobs still validate; new compat tests cover both shapes.

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