docs(issue): route agent tracker writes through the dedicated claude account

Agent-driven tracker writes previously authenticated as the repository
owner, making agent actions indistinguishable from the owner's own in
tracker history. A dedicated Gitea user `claude` now exists with
collaborator access; the issue skill documents the actor-identity rule
and the credential location.

refs #26

issue/SKILL.md

@@ -243,6 +243,18 @@ the repository from the git remote; override with `--repo owner/name`
 when running outside the repo (the project's issue tracker — its
 CLAUDE.md project facts name the repo slug and the list/show commands).
 
+### Actor identity
+
+Agent-driven tracker writes — create, edit, comment, close, re-label,
+milestone changes — run under the dedicated Gitea user `claude`, not
+the repository owner, so tracker history distinguishes agent actions
+from the owner's own. The `claude` credentials live in
+`~/.claude/gitea-claude.env` (`GITEA_URL`, `GITEA_TOKEN`) and are used
+via the Gitea REST API. tea's own config remains the owner's login:
+reads may run under either identity, but an agent performing a write
+authenticates with the `claude` token. The account needs collaborator
+(write) access on a repository before it can act there.
+
 | Operation | Command |
 |---|---|
 | List open | `tea issues ls --state open` |