Trimmed the Redis streams by retention on every append.

[moedash]

This PR trims the Redis provider's logs by age, and optionally by count, on every append.

What changed?

• RedisStreams(retention=, max_len=), with DEFAULT_RETENTION at seven days and no count cap by default. Both are checked at construction.
• The append script trims exactly, in the same call as the append. A stage at or above max_len is refused where it's staged.
• A replay that reaches a trimmed range fails its task with StreamIntegrityError, which the transport no longer wraps as a storage error. An outside cursor below the window is refused with StreamCursorError.
• Tests for the bounds, the default, the loud replay failure, the age trim and the batch the window can't hold.

Part of AI-198 (epic AI-37).

Why?

Without a trim, a Redis log grows forever. The trim has no consumer floor, because keeping one would need a consumer registry in Redis. So the failure modes are made loud instead: a replay past the window fails rather than replaying something else. Trims are exact because Redis's approximate trim never touches a log shorter than one macro node.

How did you test it?

Link to a test plan if any -

• Unit Tests
• Staging
• End to End Tests

poe lint is clean. The external stream suite passes on the dev server. The streams suite with STREAMS_LIVE=redis passes against a channel server and a local Redis.