fix(bridge): split notification cache lock

[vcheckk]

Closes #104.

What changed

• Splits notification-cache access out of the translator lock path to reduce notification pump starvation.

Validation

• Included in standalone integration branch restart-standalone-integration.
• cargo test -p mcpls-core passed.
• cargo clippy -p mcpls-core --all-targets -- -D warnings passed.
• Real rust-analyzer smoke passed: cargo test -p mcpls-core --test integration_tests integration::rust_analyzer_tests::test_hover_on_u64_type -- --ignored --exact --nocapture.

[bug-ops]

Closing this PR as part of a batch closure of all submissions from this contributor.

The entire set of 15 PRs (#180–#194) was submitted within ~3 minutes on 2026-06-13, indicating AI-generated code submitted without proper individual review or integration into the project's contribution workflow.

Specific issues identified across the batch:

• PRs opened against issues explicitly marked as blocked (e.g. fix(bridge): split notification cache lock #180 closes fix(bridge): split NotificationCache out of Translator lock to eliminate notification_pump starvation #104 which is blocked by Document tracker never re-reads files after first didOpen — every external edit yields stale results #102)
• Nested mutex anti-patterns introduced (perf(bridge): remove translator mutex from tool requests #181: Mutex inside Mutex)
• Incomplete refactors (read_resource contention path not updated in fix(bridge): split notification cache lock #180)
• Breaking API changes without coordination (feat(config): route tools to named LSP servers #194 changes registration key from language_id to server_key)
• Stacked PRs submitted as independent PRs without proper base branch setup

If you would like to contribute to this project, please open individual issues for discussion before submitting code, and follow the contribution guidelines.