feat(daemon): add paginated Slack channel history

[zfy0701]

Summary

• expose Slack conversations.history as a bounded daemon read port and MCP getChannelHistory tool
• forward cursor and timestamp bounds, returning hasMore and nextCursor for agent-driven pagination
• surface only bounded Slack API error codes to the agent

Validation

• daemon typecheck
• 169 focused daemon tests passed
• Prettier check passed
• pre-push ESLint passed with two existing warnings in workspace-git-write.test.ts

Created by Codex . GPT-5

[agentconnect-md-test]

Requesting changes for one blocking regression on c6d5713.

Declaring Slack channel history at the platform level exposes getChannelHistory to every Slack-backed session, including Collaboration Arena sessions, but VirtualSlackConnection was not extended with that consumed read port. The current Unit Test check fails in evals/test/connection-surface.test.ts with VirtualSlackConnection is missing concrete-connection members: getChannelHistory. This is also a runtime mismatch: an Arena agent is shown the tool, then receives “channel history is unavailable on this connection” when it calls it.

Please implement the corresponding bounded/paginated virtual history read (and any world-port support it needs) so the concrete and virtual Slack surfaces remain aligned. Build, Check, image, sandbox, and integration checks are green; the only observed CI failure is this directly related Arena surface guard. Local execution was unavailable because this checkout has no installed dependencies, so validation used exact-head source inspection and the current GitHub Actions logs.

_{sent by review-bot (Codex · gpt-5.6-sol) · open in session}

[agentconnect-md-test]

Blocking: this capability declaration injects getChannelHistory into every Slack session, but VirtualSlackConnection does not implement the method. The existing Arena surface guard is failing on this head (missing concrete-connection members: getChannelHistory), and evaluation agents receive a tool that can only throw “unavailable on this connection.” Please add the bounded/paginated virtual read-port implementation (and world history support) so virtual Slack stays in parity with the daemon-consumed concrete surface.