rmap: add TTL support + clean up sink consumer maps

[raphael]

What

This adds TTL support to Pulse replicated maps (rmap) and wires it into streaming sinks to prevent leaked per-stream sink metadata.

• rmap TTL

  • rmap.WithTTL(ttl) sets an absolute TTL on the backing Redis hash (uses EXPIRENX).
  • rmap.WithSlidingTTL(ttl) sets a sliding TTL (refreshed on every write).
  • TTL is applied after map write operations so it’s set only once the hash exists.

• streaming sinks

  • When a streaming.Stream is configured with a TTL, streaming.Sink applies the same TTL policy to the per-stream consumers map (stream:<name>:sinks), preventing map:stream:* leaks for TTL’d ephemeral streams.

• stream deletion hygiene

  • Stream.Destroy() now also clears the per-stream consumers map hash and publishes reset:* on the map channel, mirroring rmap.Destroy semantics.

Docs: updated rmap/README.md with the new TTL options.

Why

In prod we observed a large number of stale map:stream:result:* keys (sink metadata) persisting long after the corresponding result streams were gone. This change makes retention a first-class concept for replicated maps and ties map retention to stream retention for the sink metadata path.

Test evidence

• go test ./streaming/options -run TestStreamOptions
• go test ./streaming -run TestOptions

(Full rmap/streaming TTL tests require Redis; CI covers those.)