docs(agents): scaffold docs/agents/ skill config files

- docs/agents/issue-tracker.md — GitHub, gsd-build/get-shit-done, .envrc token required
- docs/agents/triage-labels.md — confirmed=AFK-ready, approved-*=human-ready, needs-reproduction=needs-info
- docs/agents/domain.md — single-context, CONTEXT.md sections explained
- CLAUDE.md — fix stale triage label (needs-maintainer-review doesn't exist),
  fix stale domain note ('neither exists yet'), add .envrc token reminder to issue tracker summary

docs/agents/issue-tracker.md

@@ -0,0 +1,32 @@
+# Issue tracker: GitHub
+
+Issues for this repo live in **GitHub Issues** at `gsd-build/get-shit-done`.
+
+## Auth
+
+Always read the token from `.envrc` — never use the ambient `gh auth` session (it resolves to enterprise credentials that cannot access this repo):
+
+```bash
+export GITHUB_TOKEN=$(grep GITHUB_TOKEN .envrc | cut -d\' -f2)
+# or inline:
+GITHUB_TOKEN=$(grep GITHUB_TOKEN .envrc | cut -d\' -f2) gh issue create ...
+```
+
+## Conventions
+
+- **Create**: `gh issue create --repo gsd-build/get-shit-done --title "..." --body "..."`
+- **Read**: `gh issue view <number> --repo gsd-build/get-shit-done --comments`
+- **List**: `gh issue list --repo gsd-build/get-shit-done --state open --json number,title,labels --jq '...'`
+- **Comment**: `gh issue comment <number> --repo gsd-build/get-shit-done --body "..."`
+- **Label**: `gh issue edit <number> --repo gsd-build/get-shit-done --add-label "..." --remove-label "..."`
+- **Close**: `gh issue close <number> --repo gsd-build/get-shit-done --comment "..."`
+
+Always pass `--repo gsd-build/get-shit-done` explicitly — the local clone has multiple remotes and `gh` may resolve to the wrong one.
+
+## When a skill says "publish to the issue tracker"
+
+Create a GitHub issue at `gsd-build/get-shit-done`.
+
+## When a skill says "fetch the relevant ticket"
+
+Run `gh issue view <number> --repo gsd-build/get-shit-done --comments`.