Workspace header reads "Finished" for a rejected/expired gated request notice (_portal_body) #3688

Problem

After #3657 (#3653), a gated request's ending is reported back in the requester's own chat. When that chat is a Workspace thread, the notice goes through channel_completion_report._portal_body, whose header is chosen only by whether the wake-up row ran to completion:

head = f"**Finished{who}**" if done else f"**Didn't finish{who}** — {status}"

A wake-up row that reports a rejected, expired or not-run gate outcome completes normally, so the Workspace reader sees:

**Finished** | | Your request was rejected.

with the "done" pill — the first word the requester reads says the opposite of what happened. The PR body for #3657 discloses this; the merge-train validator executed the delivery leg (report_completion → _resolve_portal → add_portal_message) and confirmed the rendered body.

Expected

A skill_gate-triggered wake-up row (the ending notice, not the approved run itself) gets a neutral header in _portal_body — the outcome sentence already carries the verdict — or the header is derived from the gate outcome, not from the row's run status.

Where

• src/backend/services/channel_completion_report.py — _portal_body, the head = ... line.
• The row is identifiable: it is created by skill_gate_service._wake_requester_agent with the Gated skill: the person who asked never sees the outcome in their chat; the requesting agent's wake-up run carries no channel context #3653 dispatch context.

Acceptance

• A rejected / expired / not-run gate notice in a Workspace thread does not read "Finished".
• The approved-run's own completion notice is unchanged.
• A test drives a skill_gate wake-up row through the real report_completion → portal path and asserts the header.

Found during the 2026-10-14 merge-train validation of #3657 (non-blocking there).