feat(skills): a consumption-skill template with no defaults

A per-corpus skill copies this directory and fills every <PLACEHOLDER>. None of
them has a default: a corpus's budget, instrument, profile name and conditional
fields are facts about that corpus, and a default would be this repository
asserting one it has not measured.

The section headings are fixed because the checker in the next commit reads
them by name. references/example-payload.json is the known-positive that keeps
a refuse-everything checker from passing.

skills/okf-consume-template/references/example-payload.json

@@ -0,0 +1,59 @@
+{
+  "contract": "okf-consumption/1",
+  "bundle": {
+    "bundle_id": "example-corpus",
+    "ref": "9dd86b1f0c2e4a7b8d3f5061a2c4e6809bdf1357"
+  },
+  "budget": {
+    "unit": "o200k_base tokens",
+    "instrument": "<BUDGET_INSTRUMENT>",
+    "limit": 30000,
+    "spent": 18412,
+    "known_positive": {
+      "case": "commons reference document",
+      "expected": 10406,
+      "measured": 10406
+    }
+  },
+  "denominators": {
+    "considered": 5,
+    "withheld": 2,
+    "delivered": 3
+  },
+  "excerpts": [
+    {
+      "bundle_id": "example-corpus",
+      "concept_id": "fire-compartmentation-3-1",
+      "path": "concepts/fire-compartmentation-3-1.md",
+      "sha256": "39ccd5fdef696327c9b8bed873cb5d085fc2460e9a01cd12f872488cd8c74580",
+      "adjudication": "adjudicated",
+      "trust_tier": "human-reviewed"
+    },
+    {
+      "bundle_id": "example-corpus",
+      "concept_id": "escape-routes-3-2",
+      "path": "concepts/escape-routes-3-2.md",
+      "sha256": "4352bb77959800ef35bb2b7afd82fbe764a93adc4252d635263388c8ef8811a6",
+      "adjudication": "proposed",
+      "trust_tier": "machine-confirmed"
+    },
+    {
+      "bundle_id": "example-corpus",
+      "concept_id": "scope-1-0",
+      "path": "concepts/scope-1-0.md",
+      "sha256": "735ee94323f323b17bb567b9f02fa0926ade222f520c66641581e9be3c007088",
+      "adjudication": "unknown",
+      "trust_tier": "unverified"
+    }
+  ],
+  "withheld": [
+    {
+      "concept_id": "appendix-a-tables",
+      "rule": "over budget after knapsack"
+    },
+    {
+      "concept_id": "revision-log",
+      "rule": "type not in question scope"
+    }
+  ]
+}