fix(runtime): recover plugin hook lock poison - #7420

Summary

• route the plugin state-file advisory-lock registry through a poison-recovery helper
• route every persistent hook-process pool access through a second recovery helper
• preserve active lock and process slots, log each recovery, and clear poison for subsequent ordinary access
• cover both registries with real held-lock panic regressions, including the production health-check path
• merge the latest origin/main before final verification

Verification

• CARGO_TARGET_DIR=/private/tmp/librefang-target-pr7420-final cargo test -p librefang-runtime plugin_runtime::tests --lib — 28 tests passed
• CARGO_TARGET_DIR=/private/tmp/librefang-target-pr7420-final cargo clippy -p librefang-runtime --all-targets -- -D warnings
• cargo fmt --all -- --check
• git diff --check origin/main...HEAD

Out of scope

• cross-process state-file locking
• hook subprocess lifecycle, retry policy, sandbox policy, and registry capacity
• other poisoned-lock domains listed in the audit handoff