Separate pure session reads from liveness reconciliation and cleanup

[schickling-assistant]

Problem

getSession(ref) calls listSessions(), even when ref is an immutable session ID. listSessions() scans the full registry, probes every socket, removes stale socket/PID files, and deletes old or invalid metadata.

This makes a metadata lookup:

• O(number of sessions), including sequential socket probes;
• effectful, because a read can perform cleanup;
• unsuitable for frequent consumers such as statuslines and dashboards.

A local registry with about 1,000 metadata records took several minutes for one pty list --json call when socket probes hit their timeout path. Reading the exact metadata file directly was effectively immediate.

Desired contract

Expose distinct operations:

get(id)       pure exact metadata read; no scan, probe, or cleanup
snapshot()    pure registry snapshot; no probe or cleanup
probe(id)     explicit liveness/socket reachability check
gc()          explicit reconciliation and cleanup

Display-name resolution can remain a separate lookup that reports ambiguity. Exact immutable-ID lookup should not fall back to a full scan.

Metadata snapshots remain the state source. Events can invalidate caches, but a missed or compacted event must be recoverable through a pure snapshot read.

Posted on behalf of @schickling

field	value
agent_identity	dev3.direct.omp.zf8bz8y7
session	dev3.zf8bz8y7
agent_persona	generalist
agent_supervisor	unavailable
agent_tool	OMP
agent_tool_version	18.1.2
agent_runtime	OMP 18.1.2
tooling_profile	dotfiles@7534055