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/research/SKILL.md

@@ -0,0 +1,12 @@
+---
+name: research
+description: Investigate a question against high-trust primary sources and capture the findings as a Markdown file in the repo. Use when the user wants a topic researched, docs or API facts gathered, or reading legwork delegated to a background agent.
+---
+
+Spin up a **background agent** to do the research, so you keep working while it reads.
+
+Its job:
+
+1. Investigate the question against **primary sources** — official docs, source code, specs, first-party APIs — not a secondary write-up of them. Follow every claim back to the source that owns it.
+2. Write the findings to a single Markdown file, citing each claim's source.
+3. Save it where the repo already keeps such notes; match the existing convention, and if there is none, put it somewhere sensible and say where.