Make INDEX/routing-surface consistency a CI-checked invariant, not an authoring discipline

[SUaDtL]

Summary

The one-line surface summaries the orchestrator routes by (skills INDEX.md, agents INDEX.md, routing-table.md) are documentation, and documentation drifts from the bodies it describes. Today nothing mechanical detects that drift; the failure mode is silent misrouting. Add a CI check that fails when a surface entry and its body disagree.

Evidence

• Documentation-drift literature at scale: code and comments co-evolve in ~90% of change events, but the doc update frequently lands in later commits or never (Wen et al., ICPC 2019, https://dl.acm.org/doi/abs/10.1109/ICPC.2019.00019; outdated-docs detection, https://arxiv.org/abs/2307.04291). A 23-skill / 28-agent index is the same artifact class.
• The cost is amplified here because the index is not passive documentation: it is the routing surface. "Skill bodies load on routing only" means a stale one-liner can send the orchestrator to the wrong skill, and the model consulting routing-table.md inherits the miss (NoLiMa shows association from sparse descriptions is exactly where models are weakest, https://arxiv.org/abs/2502.05167).
• This was flagged as the clearest open gap in the 2026-08-03 context-architecture research review (dossier in the arbiterforge-site repo, .codearbiter/research/2026-08-03-dossier-4-context-architecture.md): the pattern's known failure modes are retrieval-miss and index staleness, and staleness currently has no in-place mitigation.

Proposed checks (in ascending strength; pick during implementation)

1. Inventory parity: every skill/agent on disk has exactly one INDEX row and every INDEX row has a body; routing-table.md routes only to things that exist. Pure structural check, zero false positives; do this first.
2. Ownership-claim parity: each INDEX row's "routed to by" / "owns" claims cross-checked against the body's frontmatter or a declared owns:/routed-by: field, so the claim is generated or verified rather than hand-maintained.
3. Derived one-liners: generate INDEX rows from skill frontmatter (description field) at build time, the same way multi-host surfaces are already generated from core/. Drift becomes impossible rather than detected.
4. Optional freshness tripwire: fail CI when a SKILL.md changes without its INDEX row or routing-table entry being touched in the same PR (suppressible with an explicit marker for genuinely no-op body edits).

Acceptance criteria

• Check level chosen and recorded (1-4 above); rationale noted
• CI job fails on a seeded drift fixture (mutated one-liner, orphan row, missing row, dangling route)
• Runs across all generated host surfaces (ca, ca-codex, ca-pi) so parity holds everywhere
• skill-author routing-integration phase updated to reference the mechanical check

Origin

2026-08-03 research sweep for the arbiterforge.com "Why hard gates" essay; sibling of #591 (STE-inspired normative authoring) and the blocking-vs-reminder hook classification issue.