Close the Unattended Loop's Parking-Comment and Interrupted-Park Gaps #2184

Left over from the local review passes on the #1812 change to .agents/skills/unattended-handoff/SKILL.md. The maintainer chose to narrow that change and file these rather than keep re-wording them there, since each added sentence drew new findings.

• A link can hold more than one parking comment. Worker step 1 reads "the parking comment", singular. A link that was parked, unblocked in place by taking blocked off it, and parked again carries two. A worker following the older one follows an answered decision and meets the newer question again, and since that decision issue is closed, "Parking" step 2's duplicate check misses it and the worker re-asks a question already answered. Likely fix: "the newest parking comment".
• A worker interrupted between "Parking" steps 3 and 4 leaves a link with a parking comment and no blocked label. The picker then treats it as a lane whose worker died, and the next worker has no instruction for a waited-on decision that is still unanswered. An attempt keyed on where the comment sits and whether the issue still carries decision could not tell this from a maintainer who unblocked the link in place, and the handoff's label history is what separates the two.
• The promotion STOP never reads which promotion pull request is open. A decision issue naming a promotion that was since closed and replaced reads the same as one naming the open promotion. This predates unattended-handoff: adopted lesson issues stall, and the promotion STOP matches any decision issue #1812.

Done looks like: each gap closed in the skill, or declined with its reason, with a local review pass reaching no finding on the text the fix writes.