feat(events): add SdkErrorCode typed mapping for SDK error integers

[devin-ai-integration]

Summary

Error::CommandFailed, Error::ClientError, and the FfiError::SdkError variant previously carried the SDK's integer nErrorNo as a raw i32, so callers had to memorise the CMDERR_* / INTERR_* numeric constants or pull in teamtalk_sys::ClientError directly. This PR adds a typed view on top of the existing numeric field without changing any public struct layout (strictly additive — no downstream breakage).

New API (all in teamtalk::events):

• SdkErrorCode enum (#[non_exhaustive]) with one variant per CMDERR_* (1000–3999) and INTERR_* (10000–19999) from teamtalk_sys::ClientError, plus Success (0) and Unknown(i32) for forward-compat with future SDK releases.
• From<i32> for SdkErrorCode — lossless; unknown codes become Unknown(code) and are never silently dropped.
• From<teamtalk_sys::ClientError> for SdkErrorCode — typed bridge from the bindings enum.
• SdkErrorCode::as_i32 / name / Display / is_command_error / is_internal_error / is_known — inspection helpers suitable for structured logging and metrics.
• Error::sdk_code(&self) -> Option<SdkErrorCode> — non-consuming accessor that returns the typed code for CommandFailed, ClientError, and Ffi(FfiError::SdkError) and None for non-SDK errors (Timeout, IoError, InitFailed, etc.).

Existing fields Error::CommandFailed { code: i32, .. } and Error::ClientError { code: i32, .. } keep their i32 layout, so no downstream code breaks. Field docs now point at Error::sdk_code.

File layout: src/events.rs (256 lines) is moved to src/events/mod.rs and the new typed mapping lives in a focused sibling src/events/sdk_error.rs. No public path changes — teamtalk::events::* still re-exports everything.

Tests: crates/teamtalk/tests/sdk_error_code_tests.rs adds 11 integration cases covering: every documented ClientError FFI variant round-trips via From<i32> + as_i32; unknown positive and negative codes preserve the raw value; is_command_error / is_internal_error classification for named variants and for Unknown(_) in and out of range; Display contains the snake_case name and the numeric code; From<teamtalk_sys::ClientError> matches From<i32>; Error::sdk_code returns Some(..) for CommandFailed, ClientError, and Ffi(SdkError) and None for the other non-SDK error variants; all name() values are unique.

Local verification: cargo fmt --all --check clean; cargo clippy --workspace --all-targets --all-features -- -D warnings clean; cargo test --workspace --all-features — all tests pass (existing + 11 new SdkErrorCode cases).

Review & Testing Checklist for Human

• Skim the variant list in crates/teamtalk/src/events/sdk_error.rs against TEAMTALK_DLL/TeamTalk.h / teamtalk_sys::ClientError to make sure no CMDERR_* or INTERR_* was missed. The test from_i32_covers_every_documented_client_error_variant iterates all 44 constants currently in the bindings, so anything missing would already fail CI.
• Confirm the choice to keep Error::CommandFailed { code: i32, .. } as i32 (with the typed sdk_code() accessor) instead of introducing a breaking change on the struct field. Rationale: keeps this PR strictly additive and reviewable in isolation; a later major-bump PR can replace the i32 field with SdkErrorCode directly if desired.
• Confirm the name of AudioPreprocessorInitFailed for INTERR_SPEEXDSP_INIT_FAILED (10003). The bindings expose it under both aliases (INTERR_AUDIOPREPROCESSOR_INIT_FAILED is documented as an alias for INTERR_SPEEXDSP_INIT_FAILED with the same value). The Rust-side name leans on the newer alias for forward compatibility.

Notes

Third P1 API improvement after the ExponentialBackoff jitter PR (#51) and the StreamTypes newtype PR (#52). Branches from clean main, independent of the other open PRs, so can be merged in any order.

Next up in the API-improvement queue: TimeoutKind enum for Error::Timeout, SecretString + zeroize for passwords in LoginParams, indexed EventBus::dispatch / Router::dispatch via HashMap, then a coverage-gap test fill-in driven by scripts/audit_teamtalk_coverage.py.

The pre-existing semver CI gate is expected to remain red; release-plz handles the eventual version bump.

Link to Devin session: https://app.devin.ai/sessions/71fdd6196cb74723a2e277bb81993a9c
Requested by: @BlindMaster24

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[devin-ai-integration]

Devin Review found 1 potential issue.

⚠️ 1 issue in files not directly in the diff

⚠️ Missing SdkErrorCode re-export from lib.rs breaks crate-root access pattern (crates/teamtalk/src/lib.rs:80)

SdkErrorCode is a new public type exposed via crates/teamtalk/src/events/mod.rs:4, but it is not re-exported from crates/teamtalk/src/lib.rs:80 where every other public type from the events module (ConnectionState, Error, Event, FfiError, Result) is re-exported at the crate root. This means teamtalk::SdkErrorCode does not resolve, and users must use the longer teamtalk::events::SdkErrorCode path — inconsistent with how the rest of the events API is consumed. This violates the AGENTS.md rule: "Keep public API surface shallow: expose through lib.rs and module mod.rs."

View 3 additional findings in Devin Review.