[Docs] Sync public guides with recent shipped behavior

[roomote-community]

​Created by Roomote. View the task or mention @roomote for follow-up asks.

What changed

• document how Merge Announcer handles GitHub pull request context and links
• describe Session transcript search and highlighted excerpts
• cover Notion database properties retained in Memory
• state the Roomote Cloud trial inference allowance
• update the final setup flow to describe its single starter-task Session

Why this change was made

These user-facing behaviors shipped during the latest 24-hour merge window, but their public guides were missing details or still described the previous behavior.

Impact

Public documentation now matches the current setup, Sessions, Memory, inference, and automation experience. There is no runtime behavior change.

Screenshots

[roomote-community]

No code issues found. See task

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