[Docs] Explain repository-owned agent instructions

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• documented how Roomote's repository workflows discover scoped AGENTS.md guidance
• clarified the generated shared-workspace AGENTS.md role without implying that it replaces repository instructions
• limited CLAUDE.md discovery and precedence claims to the environment-setup workflow where they are explicitly supported
• explained why AGENTS.md is the portable repository-owned source for mixed-model and mixed-harness teams

Why this change was made

Roomote already guides task agents through repository-owned instruction hierarchies, but the public environment documentation did not explain the behavior or its scope. Users should be able to centralize portable repository rules without relying on undocumented assumptions or duplicating guidance for each compatible agent tool.

Impact

Users can now see which repository instruction files Roomote workflows inspect, how scoped guidance is resolved during environment setup, and which higher-priority instructions repository guidance cannot override. This is documentation-only and does not change runtime behavior.

Screenshots

[roomote-community]

No code issues found. See task

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