feat: Add ATAM semantic anchor

[Copilot]

Adds ATAM (Architecture Tradeoff Analysis Method) as a semantic anchor under the Software Architecture category.

New files

• docs/anchors/atam.adoc — English anchor covering: Utility Tree, Quality Attribute Scenarios, Sensitivity/Tradeoff Points, Risks/Non-risks, and the nine-step ATAM process
• docs/anchors/atam.de.adoc — German translation

Updated

• docs/all-anchors.adoc — ATAM included in Software Architecture section (alphabetical order, between arc42 and c4-diagrams)

Metadata (auto-generated via npm run build):

• Category: software-architecture
• Roles: software-architect, team-lead, product-owner
• Proponents: Rick Kazman, Mark Klein, Paul Clements (SEI / Carnegie Mellon)
• Related: arc42, adr-according-to-nygard

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Anchor Proposal]: ATAM</issue_title>
<issue_description>### Proposed Term

ATAM

Context (Optional)

No response

Pre-submission Checklist

• I have searched existing anchors and this term is not already included
• This term refers to a well-established concept (not something I invented)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Anchor Proposal]: ATAM #133

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