docs: enforce Model Used section in PR descriptions (#2891)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Agents create pull requests as part of their development workflow
> - The PR template already has a "Model Used" section (added in PR
#2552)
> - But agents were not filling it in because neither AGENTS.md nor
CONTRIBUTING.md referenced it
> - This PR updates both docs to explicitly require reading and filling
in the full PR template, including Model Used
> - The benefit is that every PR will now document which AI model
produced the change, improving traceability and auditability

## What Changed

- **CONTRIBUTING.md**: Added "Model Used (Required)" subsection under
"PR Requirements (all PRs)" and listed it in the required sections
enumeration
- **AGENTS.md**: Added new "Section 10: Pull Request Requirements"
instructing agents to read and fill in every section of the PR template
when creating PRs (including Model Used). Renumbered "Definition of
Done" to Section 11 and added PR template compliance as item 5.

## Verification

- Review `CONTRIBUTING.md` — confirm "Model Used (Required)" subsection
appears under PR Requirements
- Review `AGENTS.md` — confirm Section 10 (Pull Request Requirements)
lists all required PR template sections including Model Used
- Review `AGENTS.md` — confirm Definition of Done item 5 references PR
template compliance
- No code changes, no tests to run

## Risks

- Low risk — documentation-only changes. No code, schema, or behavioral
changes.

## Model Used

- **Provider**: Anthropic Claude
- **Model ID**: claude-opus-4-6 (1M context)
- **Capabilities**: Tool use, code execution, extended context

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

Co-authored-by: Paperclip <noreply@paperclip.ing>

AGENTS.md

@@ -138,7 +138,18 @@ When adding endpoints:
 - Use company selection context for company-scoped pages
 - Surface failures clearly; do not silently ignore API errors
 
-## 10. Definition of Done
+## 10. Pull Request Requirements
+
+When creating a pull request (via `gh pr create` or any other method), you **must** read and fill in every section of [`.github/PULL_REQUEST_TEMPLATE.md`](.github/PULL_REQUEST_TEMPLATE.md). Do not craft ad-hoc PR bodies — use the template as the structure for your PR description. Required sections:
+
+- **Thinking Path** — trace reasoning from project context to this change (see `CONTRIBUTING.md` for examples)
+- **What Changed** — bullet list of concrete changes
+- **Verification** — how a reviewer can confirm it works
+- **Risks** — what could go wrong
+- **Model Used** — the AI model that produced or assisted with the change (provider, exact model ID, context window, capabilities). Write "None — human-authored" if no AI was used.
+- **Checklist** — all items checked
+
+## 11. Definition of Done
 
 A change is done when all are true:
 
@@ -146,6 +157,7 @@ A change is done when all are true:
 2. Typecheck, tests, and build pass
 3. Contracts are synced across db/shared/server/ui
 4. Docs updated when behavior or commands change
+5. PR description follows the [PR template](.github/PULL_REQUEST_TEMPLATE.md) with all sections filled in (including Model Used)
 
 ## 11. Fork-Specific: HenkDz/paperclip
 

CONTRIBUTING.md

@@ -37,7 +37,11 @@ PRs that follow this path are **much** more likely to be accepted, even when the
 
 ### Use the PR Template
 
-Every pull request **must** follow the PR template at [`.github/PULL_REQUEST_TEMPLATE.md`](.github/PULL_REQUEST_TEMPLATE.md). If you create a PR via the GitHub API or other tooling that bypasses the template, copy its contents into your PR description manually. The template includes required sections: Thinking Path, What Changed, Verification, Risks, and a Checklist.
+Every pull request **must** follow the PR template at [`.github/PULL_REQUEST_TEMPLATE.md`](.github/PULL_REQUEST_TEMPLATE.md). If you create a PR via the GitHub API or other tooling that bypasses the template, copy its contents into your PR description manually. The template includes required sections: Thinking Path, What Changed, Verification, Risks, Model Used, and a Checklist.
+
+### Model Used (Required)
+
+Every PR must include a **Model Used** section specifying which AI model produced or assisted with the change. Include the provider, exact model ID/version, context window size, and any relevant capability details (e.g., reasoning mode, tool use). If no AI was used, write "None — human-authored". This applies to all contributors — human and AI alike.
 
 ### Tests Must Pass