feat(config)!: expose DocumentTracker resource limits via workspace config

[bug-ops]

Summary

• Add workspace.max_documents/workspace.max_file_size TOML config fields so operators can raise DocumentTracker's previously hardcoded caps (100 open documents, 10MB max file size) for larger or longer-running agent sessions. 0 disables either limit; omitting a field preserves today's defaults. WorkspaceConfig::resource_limits() maps the fields onto bridge::ResourceLimits, and a new Translator::with_resource_limits builder wires the resolved limits into serve()'s Translator construction alongside the existing with_extensions builder — the two now read each other's already-set field when rebuilding document_tracker, so they compose in either order without one silently discarding the other's effect. DocumentLimitExceeded/FileSizeLimitExceeded error messages gained a static hint pointing at the relevant config field.
• Rename NotificationCache::get_logs/get_messages to logs/messages, dropping the redundant get_ prefix per the Rust API Guidelines (get_diagnostics is a keyed lookup and is unchanged).

Breaking changes

• NotificationCache::get_logs/get_messages renamed to logs/messages.
• ResourceLimits is now re-exported from bridge (previously private to bridge::state), making the already-pub DocumentTracker::new constructible from outside the crate for the first time.

Test plan

• cargo +nightly fmt --all -- --check
• cargo clippy --all-targets --all-features --workspace -- -D warnings
• cargo nextest run --workspace --all-features --lib --bins (653 passed, 1 skipped)
• RUSTDOCFLAGS="-D warnings" cargo doc --no-deps --all-features
• New unit tests: TOML defaults/overrides, max_file_size: 0 unlimited, resource_limits() mapping, TOML round-trip, Translator::with_resource_limits/with_extensions order-independence (verified via language resolution through a non-empty extension map, not just the limit value)
• Updated docs/user-guide/configuration.md and CHANGELOG.md

Closes #315, closes #293