[TD-08] `Arc<Mutex<>>` in search/handle could be `Arc<RwLock<>>`

[intendednull]

Audit finding from #300 (commit 679f9fe)

Severity: low
Category: tech debt / performance
File: crates/client/src/search/handle.rs:29-32 ; crates/web/src/state_bridge.rs:23 ; crates/client/src/{listeners.rs:28, mutations.rs:47}
Obvious fix: yes for index; no for state_bridge.rs

Description

12 Arc sites total. The search handle wraps four fields each in an Arc — for a read-mostly index (queries vastly outnumber inserts) an Arc<RwLock> would let multiple lookups proceed concurrently. The state_bridge.rs doc-comment even calls out the choice as deliberate-for-mutation, but reads dominate the actual call sites.

Impact / Threat

Maintenance, performance — clarifies intent and removes unnecessary lock contention on the search hot path.

Suggested fix

Switch index and config in search/handle.rs to Arc<RwLock>. Keep status as Mutex since it's small and write-on-completion.

Verify

rg "Arc<Mutex" --type rust crates/ | wc -l
rg "Arc<Mutex" crates/client/src/search/handle.rs

[intendednull]

already-fixed. audit premise moot — crates/client/src/search/handle.rs migrate to SearchActor in 64417e2 (PR landed during phase-2e). no more Arc<Mutex<_>> quartet; cross-field updates atomic via mailbox FIFO.

verify @ crates/client/src/search/handle.rs:29-33 (now addr: Addr<SearchActor>) + crates/client/src/search/actor.rs:4 ("Replaces the prior Arc<Mutex<_>> quartet in [super::handle].").

close as not_planned — audit's Arc-shape concern superseded by actor migration, no Arc swap needed.

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