DRU-389 - Issue board doors: create, move, edit, comment

[chaosk]

Linear ticket: DRU-389

Stacked on DRU-388.

Summary

• Write doors mount under /api/software_factory as /ticket-projects and /tickets. Unprefixed operation_ids derive to software_factory_create_ticket, software_factory_get_ticket, software_factory_add_comment, …
• Create and content edits stay quiet. set_status is the only publisher: one ticket.transitioned with source="issues" and display labels; a repeat of the current status publishes nothing.
• Comment author is the request account, never a client field.

Test plan

• uv run ruff check backend
• uv run ruff format --check backend
• uv pip install -e backend/tests/druks-field_notes
• uv run pytest backend/
• Create does not publish, including create-into-Ready for Agent.
• set_status publishes once with source="issues" and display labels; a second call with the same status publishes nothing.
• Done → completed and terminal true; Cancelled → terminal true, completed false.
• /mcp lists software_factory_get_ticket and software_factory_add_comment, not issues_*.
• 4xx on empty title/body, unknown identifier, and the system assignee.

Pages and the Software Factory tracker stay on later tickets.