fix(plugin-redis): throw on unexpected operation instead of crashing the host

[datlechin]

Summary

Phase 9 (R-009): remove a user-triggerable host crash from the Redis driver. The 7 default: fatalError("Unexpected operation in execute…Operation") branches in RedisPluginDriver now throw RedisPluginError(code: 0, message: …). The dispatch methods are already async throws, so an unexpected operation surfaces as a normal query error instead of crashing the whole app via fatalError.

Risk Addressed

• R-009: plugin runtime path guarded by fatalError could take down the host process.

Verification

• xcodebuild -scheme RedisDriver build succeeds.
• Line-neutral change (one fatalError line → one throw line each); no behavior change on the happy path.

Notes

• ABI bump required: no (plugin internals only, no protocol change). Bundled plugin, ships with the next app build.
• Docs updated: no.
• No CHANGELOG entry: these are unreachable defensive default: branches, so there is no observable behavior change.
• Pre-existing swiftlint --strict warnings in this file (file_length 1426, plus an implicit_return/vertical_whitespace on untouched lines) are out of scope; this change doesn't add or remove lines.