Add scope-aware memory providers

[16francej]

Add scope-aware memory routing so deployments can combine the built-in notebook with external MCP-backed providers and independently configure recall, explicit writes, automatic capture, and management by scope.

• passes query and acting-user context into recall
• supports separate read/write OAuth credentials, bounded calls, and fail-open recall
• preserves existing notebook behavior by default
• verification: focused memory/config/MCP tests, typechecks, lint, and orchestrator suite

Implements the direction proposed in #600.

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[time-attack]

Thanks for this, @16francej — and sorry for the slow response.

We're closing this PR. Per CONTRIBUTING.md, since coding agents write most of the underlying code now, we'd rather receive feature ideas as a short human-written note in adrs/ — informal is great, just the idea in your own words — and bugs as a plain issue. If we're aligned we're happy to burn our own tokens on the implementation, and we'll credit you as co-author.

We don't want your idea to get lost, so we've captured it in #726 to triage on our side. Please feel free to open an adrs/ note if you feel strongly about the approach. Appreciate you engaging with the repo!