battery-service: minimize panic code paths

[jerrysxie]

This pull request refactors error handling and buffer copying logic in the battery service code to make it more robust and explicit. The main improvements are in the way slices are copied into fixed-size buffers and how errors are handled and propagated in the state machine.

Buffer copying improvements:

• Refactored the buffer copying logic in compute_bix (acpi.rs) to use safer and more explicit slice operations with get_mut and ok_or, replacing the previous use of try_into and direct indexing. This reduces the chance of panics and makes error handling clearer.

Error handling and state machine robustness:

• Updated the state machine timeout handling in Context (context.rs) to properly propagate errors: now, if the state machine returns an error, it sends a StateError instead of assuming infallibility.
• Changed the handling of BatteryEventInner::Oem events to return a specific InvalidActionInState error instead of an unimplemented panic (todo!()), making the state machine more robust and explicit about unsupported actions.

[Copilot]

Pull request overview

This PR refactors error handling in the battery service by removing expect() calls and replacing todo!() macros with proper error handling, making the code more robust and production-ready.

Key Changes:

• Replaced expect() with explicit match-based error handling in the timeout path
• Implemented error handling for the OEM event case instead of using todo!()
• Added clippy suppression attributes for intentional slice indexing operations

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
battery-service/src/context.rs	Replaced panic-inducing expect() with proper error propagation; implemented error handling for OEM events
battery-service/src/acpi.rs	Added clippy allow attributes to suppress false-positive warnings on bounds-checked slice operations

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

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[williampMSFT]

[jerrysxie]

Bypassed policy to merge as the entire battery team is on vacation.