Smoke the agent loop: fix the in-progress triage row #41

Part of #22. PR #39 and PR #40 already put the loop contract on main. This issue is the remaining checkbox: one docs-only smoke.

Goal

Repair the in-progress row in the triage label table. That one-line docs change is the smoke of the agent loop.

Allowed scope

docs/agents/triage-labels.md

Success criteria

• The in-progress row uses the same pipe separators as the five rows above it. The words in that row stay as they are.
• The pull request includes Fixes #41, stays inside the Allowed scope, and passes Plan Gate.
• A human reviews it as CODEOWNERS and merges it. That merge finishes the sequence: label, claim, branch, docs change, pull request, review, merge.

Do not change Plan Gate, the hook, or any other file.