Add endpoint to create new Collectives

Look at the existing tools in ex_app/lib/all_tools/collectives.py to see the pattern for calling Collectives OCS endpoints. The new create_collective tool needs to make a POST request to /ocs/v2.php/apps/collectives/api/v1.0/collectives with a name and optional emoji. Check the Collectives app's appinfo/routes.php for the exact endpoint definition. Ensure the tool requests user confirmation. Test by running the agent and verifying a new collective appears in the UI.

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Feature request

Which Nextcloud Version are you currently using: 34.0.4 (Context Agent 2.8.0, Collectives 4.6.1)

Is your feature request related to a problem? Please describe.

The Context Agent can't create a new collective, it can only work with the existing ones.

#159 added page tools in ex_app/lib/all_tools/collectives.py (list collectives, and create, edit, move and trash pages), but all of them need an existing collective_id. So a request like "create a collective for project X and add a few pages" can't be done from start to finish. A person has to create the collective in the UI first.

Describe the solution you'd like

Add a create_collective tool to collectives.py that wraps the Collectives OCS endpoint POST /ocs/v2.php/apps/collectives/api/v1.0/collectives (collective#create in the Collectives appinfo/routes.php). It should take a name and an optional emoji, and return the new collective's id.

Because creating a collective also creates a team (circle), the tool should probably be marked as needing user confirmation, like other tools that create shared resources.

Optional, maybe as a follow-up:

• a way to give the collective's team to an existing group or team (e.g. through the existing circles tools), so the result can be shared right away
• trash_collective, wrapping DELETE /collectives/{id}, with confirmation

Describe alternatives you've considered

• Creating the collective by hand in the Collectives UI.
• Having the agent write Markdown files into a normal shared folder. The result isn't a collective, so pages, backlinks and the Collectives UI don't apply.
• Creating the collective directly on the filesystem. I tested this: create_folder("/.Collectives/Test Colectivo Demo") and upload_file(".../Readme.md") both returned {"status":"success"}. But the folder never showed up in .Collectives/, a PROPFIND on it returned 404 Not Found, and no new collective appeared in search. So the files tools report success for writes that are silently dropped, and the agent can't tell that nothing was created. That's probably worth a separate bug report.

Additional context

• Related: #159 (Collectives page tools)
• The Collectives create endpoint: https://github.com/nextcloud/collectives/blob/main/appinfo/routes.php