Add writing-for-agents skill documentation and related files

- Created SKILL.md and SKILL-MECHANICS.md for writing agent skills.
- Added openai.yaml for agent interface configuration.
- Introduced AGENTS.md for agent skills overview.
- Established CONTEXT.md for personal leave planning terminology.
- Documented ordered heuristic optimization in ADRs.
- Defined personal client-side planner limitations in ADRs.
- Created domain documentation for engineering skills.
- Added issue tracker guidelines for GitLab.
- Mapped triage labels for issue tracking.
- Initialized skills-lock.json to manage skill dependencies.

.agents/skills/resolving-merge-conflicts/SKILL.md

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+---
+name: resolving-merge-conflicts
+description: "Use when you need to resolve an in-progress git merge/rebase conflict."
+---
+
+1. **See the current state** of the merge/rebase. Check git history, and the conflicting files.
+
+2. **Find the primary sources** for each conflict. Understand deeply why each change was made, and what the original intent was. Read the commit messages, check the PRs, check original issues/tickets.
+
+3. **Resolve each hunk.** Preserve both intents where possible. Where incompatible, pick the one matching the merge's stated goal and note the trade-off. Do **not** invent new behaviour. Always resolve; never `--abort`.
+
+4. Discover the project's **automated checks** and run them — typically typecheck, then tests, then format. Fix anything the merge broke.
+
+5. **Finish the merge/rebase.** Stage everything and commit. If rebasing, continue the rebase process until all commits are rebased.

.agents/skills/resolving-merge-conflicts/agents/openai.yaml

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+interface:
+  display_name: "Resolving Merge Conflicts"
+  short_description: "Resolve merge and rebase conflicts"