Feature request: add coordinator.domains: frontmatter to cloudflare:* SKILL.md files (for spec-coordinator tag-routing) #49

Context

A separate skills framework — Agent Upskill's spec-coordinator — uses an SME registry to route cross-domain spec requests to relevant skills. The registry consists of two routing layers:

1. Tag-match (deterministic) — picks skills whose coordinator.domains: [...] frontmatter overlaps the user query's tokens (confidence 1.0).
2. Sonnet classifier (fallback) — scores skills against the query via prompted classification (confidence 0.0–1.0; threshold 0.6 for picks).

In-house skills (e.g., pwa-architect, hitl-learning-architect) ship a coordinator.domains: [...] overlay so they're picked deterministically when the query matches their domain. Plugin skills like cloudflare:* currently ship without this overlay, which means they're picked classifier-only.

This works correctly today (the classifier picks cloudflare:agents-sdk, cloudflare:workers-best-practices, cloudflare:durable-objects, etc. when relevant — see agentupskill/skills-core#56 for the algorithmic clarification that ensures classifier coverage). But adding a tag-match overlay would:

• Reduce ~5 Sonnet classifier calls per spec query when a cloudflare:* skill is clearly relevant (token-overlap sufficient).
• Eliminate classifier-confidence variance (currently ±0.1 per _threshold-calibration.md F4.5) on queries where domain match is unambiguous.
• Make routing more auditable — tag-picked skills emit method: tag with a domain-list in the routing trace.

Specific request

For each cloudflare:* skill's SKILL.md frontmatter, add a coordinator.domains: [...] field listing 3–8 representative domain tokens. Suggested domains per skill (calibrated against Agent Upskill's _routing-priors.md Z2/Z3/Z5/Z6/Z14/Z17 ambiguity zones):

The coordinator: block is namespaced under a custom-coordinator key so it doesn't conflict with existing Anthropic-defined frontmatter fields. Schema (per _routing-algorithm.md §Inputs):

---
name: cloudflare:durable-objects
description: ...
coordinator:
  domains: [durable-object, stateful-coordination, websocket, alarm, sqlite-storage]
  pickable: true  # default; only set false for product-owner / invoker skills
---

Why upstream rather than a downstream patch

Plugin frontmatter ships with the plugin distribution and is not editable downstream. Without the overlay shipped in the source, every Agent Upskill installation that consults cloudflare:* SMEs falls back to classifier-only routing.

Empirical context

PR-#320 (Boogles-Playhouse/claude-skills#320) drafted an 8-PR substrate-epic spec that needed a 6-SME panel including 3 cloudflare:* skills. The classifier sweep correctly picked them post-fix (see agentupskill/skills-core#56), but tag-match would have been faster + more deterministic. F-CAL-6 in _threshold-calibration.md records the calibration trace.

Acceptance

• Each cloudflare:* SKILL.md gets a coordinator.domains: [...] block (or the umbrella one explicitly opts out).
• A short note added to the marketplace README explaining the field's consumer (Agent Upskill spec-coordinator) so future skill authors know to populate it.
• No breaking changes to Cloudflare's existing skill consumption — the field is additive.

Happy to send a PR if Cloudflare prefers that route over a maintainer-driven change.

Cross-references

• Routing algorithm: agentupskill/skills-core/spec-coordinator/references/_routing-algorithm.md
• Ambiguity zones (cloudflare-touching: Z2 PWA × Workers, Z3 system-design × DO, Z5 PWA × HITL × CF AI, Z6 umbrella × specific, Z14 mcp-builder × agents-sdk, Z17 substrate-epic): _routing-priors.md
• PR-#320 calibration: _threshold-calibration.md F-CAL-6