fix(audit): fail closed after reload errors - #7179

Changes

• turn unknown persisted audit actions into row decode failures instead of coercing them to ToolInvoke
• detach the SQLite backend after any incomplete reload so an uncertain sequence/tip cannot be persisted
• keep decoded audit rows and in-memory recording available for inspection while integrity verification remains failed
• skip anchor comparison, initialization, and updates when the durable backend was detached
• cover malformed rows and future action values with real SQLite regressions

Verification

• cargo fmt --all
• CARGO_INCREMENTAL=0 CARGO_TARGET_DIR=/tmp/librefang-target-audit-reload cargo test -p librefang-runtime-audit (41 passed)
• CARGO_INCREMENTAL=0 CARGO_TARGET_DIR=/tmp/librefang-target-audit-reload cargo clippy -p librefang-runtime-audit --all-targets -- -D warnings
• CARGO_INCREMENTAL=0 CARGO_TARGET_DIR=/tmp/librefang-target-audit-reload cargo check --workspace --lib
• git diff --check

Out of scope

• narrowing mutex scope around synchronous SQLite retention operations remains separate work
• anchor temporary-file naming and timestamp retention comparison remain separate findings