chore(agents): install mattpocock skills + per-repo agent config

- 38 skills from mattpocock/skills into .agents/skills/ (symlinked into
  .claude/skills/ for Claude Code)
- skills-lock.json for reproducible installs
- docs/agents/: issue-tracker (Gitea via tea CLI), triage-labels
  (default five-role vocabulary), domain docs (single-context)
- CLAUDE.md: add '## Agent skills' section pointing at docs/agents/
- .gitignore: un-ignore docs/agents/ under the local /docs/* rule

.agents/skills/claude-handoff/SKILL.md

@@ -0,0 +1,18 @@
+---
+name: claude-handoff
+description: Hand the current conversation off to a fresh background agent that picks up the work immediately.
+argument-hint: "What will the next session be used for?"
+disable-model-invocation: true
+---
+
+Write a handoff summary of the current conversation so a fresh agent can continue the work. Instead of saving it, launch a background agent seeded with the summary as its prompt: `claude --bg --name "<descriptive name>" "<handoff summary>"`. It starts in the current working directory and returns immediately; the user manages it with `claude agents`.
+
+Always pass `-n`/`--name` with a descriptive name (e.g. `--name "Fix login bug"`); it sets the display name shown in the job list, session picker, and terminal title.
+
+Include a "suggested skills" section in the summary, naming which skills the next agent should call the Skill tool for.
+
+Do not duplicate content already captured in other artifacts (specs, plans, ADRs, issues, commits, diffs). Reference them by path or URL instead.
+
+Redact any sensitive information, such as API keys, passwords, or personally identifiable information, since the summary becomes the agent's prompt.
+
+If the user passed arguments, treat them as a description of what the next session will focus on and tailor the summary accordingly.

.agents/skills/claude-handoff/agents/openai.yaml

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+interface:
+  display_name: "Claude Handoff"
+  short_description: "Hand off to a background agent"
+policy:
+  allow_implicit_invocation: false