bug(unic-archon-dlc): per-slice test commands cannot see a cross-slice regression

What happened

/tickets gave every slice its own test_command, filtered by story file name — CardProfileMain.parts, CardProfileMain.root, CardProfileMain.disabled and so on — precisely so each command would exercise only its own slice.

Consequence: a slice that changes a shared component's classes invalidates every earlier slice's snapshot, and no per-slice filtered command can see it. Eight stale snapshots were sitting at HEAD when the seventh slice started — three from parts, three from root, two from disabled — because an earlier slice had added hover and focus classes to the card root and never re-ran its siblings.

The author's own summary: "the narrower I made the seam, the blinder it got."

It surfaced only because a later slice happened to run a broad enough check.

What the validation does and does not do

The Nyquist map validates that every issue has a test_command. Nothing checks whether the set of commands can see a cross-slice regression. A complete set of individually-correct commands can be collectively blind, and this run produced exactly that.

The second consequence, in the Consumer

The same pressure fragmented the Storybook organisation — one component split into five story files so each slice could filter on one. See the output-organisation issue; they are two ends of one problem.

The open question

Should a slice's test_command be allowed to be narrow at all, or should the narrow command be an addition to a broad one that always runs? And what would a validation of the set rather than each member actually check?

Full evidence: docs/research/2026-08-31-dlc-run-2-findings.md.

Start with the /tickets command and the Nyquist validation described in the issue, then read docs/research/2026-08-31-dlc-run-2-findings.md. Trace how per-slice test_command values are generated and validated, including the Storybook organisation mentioned here. Done means the validation can detect cross-slice regressions rather than only confirming that each issue has a command.