fix(perps-controller): add typed position-not-found error

[abretonc7s]

Explanation

Adds PERPS_ERROR_CODES.POSITION_NOT_FOUND and returns it from HyperLiquid close, TP/SL update, and margin update when the requested position no longer exists. Clients can now distinguish an out-of-band close from unrelated provider failures without matching error text.

References

• Jira: https://consensyssoftware.atlassian.net/browse/TAT-3873
• Mobile consumer: fix(perps): reconcile positions after out-of-band closes metamask-mobile#35670

Testing

• yarn workspace @metamask/perps-controller test
• yarn build
• Prettier, scoped ESLint, and changelog validation

Checklist

• I have updated the test suite for new or updated code as appropriate
• I have updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I have communicated my changes to consumers by updating changelogs for packages I have changed
• I have introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Localized error-shape change on HyperLiquid position operations; widens PerpsErrorCode and may break callers that matched the previous error text instead of a code.

Overview
Introduces PERPS_ERROR_CODES.POSITION_NOT_FOUND as a provider-neutral code when close, TP/SL update, or margin adjustment target a symbol the venue no longer holds.

HyperLiquid now returns this code instead of free-text messages like No position found for BTC, so clients can tell an out-of-band close from other failures without parsing error strings. Tests assert the exact code; the changelog documents the new export.

Consumers with exhaustive PerpsErrorCode maps or UI that matched the old message should handle POSITION_NOT_FOUND (e.g. mobile translatePerpsError).

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