doc: add collab rules

COLLABORATING.md

@@ -0,0 +1,80 @@
+# Collaboration Rules
+
+How we work together on this project.
+
+## Honesty and Objectivity
+
+Evaluate all suggestions on their technical merits. No sycophancy — if something doesn't make sense, doesn't align with best practices, or could be improved, say so directly and constructively. Technical accuracy and project quality take precedence over being agreeable.
+
+## Core Workflow: Research → Plan → Implement → Validate
+
+Every non-trivial feature or bug fix follows this sequence:
+
+1. **Research** — Read the relevant code. Understand existing patterns before touching anything.
+2. **Plan** — Write a plan to `/.agent/current-plan.md` and align with the user before writing code. Update the plan as work progresses.
+3. **Implement** — Build with tests and error handling. Use pure functions where possible.
+4. **Validate** — Run formatters, linters, and tests after every implementation step.
+
+Never start writing code without having read the relevant files first.
+
+## Issue Tracking (Gitea)
+
+All work is tracked in **Gitea** at `http://192.168.178.71:3005` (repo `marcel/familienarchiv`). Never use todo files or CLAUDE.md notes as a substitute.
+
+Create an issue whenever work is identified that isn't being done in the current session.
+
+### Issue title formats
+
+**`feature` label** — user story format:
+```
+As a [role] I want [capability] so/because [reason]
+```
+Examples:
+- "As a user I want to search documents so I can find a specific document faster"
+- "As an admin I want to add a new user so I don't have to restart the server"
+
+**`bug` label** — user-facing impact, not the technical cause:
+```
+[What breaks] when [trigger]
+```
+Examples:
+- "Document list shows blank page when no results found"
+- "Upload fails silently when file exceeds 50MB"
+
+**`devops` label** — infrastructure, CI/CD, deployment, tooling:
+- "Fix CI checkout failing due to unresolvable hostname"
+- "Add E2E test seed data for runner"
+
+### Priority labels
+
+- `priority: high` — blocking or urgent
+- `priority: medium` — normal
+- `priority: low` — nice to have
+
+### Other labels
+
+- `needs-discussion` — decision needed before work starts
+- `wontfix` — acknowledged, not addressing
+
+## Commit Messages
+
+Every commit must reference the relevant Gitea issue.
+
+- `Closes #12` — commit fully resolves the issue (Gitea auto-closes it)
+- `Refs #12` — commit is related but doesn't fully close the issue
+
+Place the reference at the end of the commit body:
+
+```
+feat: add person typeahead to document edit form
+
+Closes #7
+Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
+```
+
+## Code Style Reminders
+
+- Pure functions over stateful helpers where possible
+- No premature abstractions — solve the problem in front of you
+- No backwards-compatibility shims for code that has no callers
+- Validate at system boundaries only (user input, external APIs)