CB-WP-0004 T04: fact registry and make facts-check — DFD gets a gate

Duplicated-fact drift is the fourth error class and the only one with no
executable rule. No positive control catches it (both copies are
internally consistent) and re-derivation does not either (the copy
reproduces whatever it was copied from). It is caught only by reading a
copy against its source, which nothing in the loop required.

facts.toml holds 15 facts and is GENERATED by `make facts-gen` from
cb-cost, dep-weight and rule-coverage. The trap this task named — a
hand-maintained registry that becomes another drifting copy — is closed
by facts-check re-running the instruments and failing when the committed
registry disagrees with them. A stale registry cannot certify stale
artifacts.

An artifact quoting a fact tags it: **$93.15** <!-- fact --> with the key.
17 occurrences across 5 artifacts are now checked.

Falsified before being believed: changing CostAccounting.md line 158 from
$93.15 to $92.87 — the exact historical drift — produced exit 1 naming
the file, the line and the expected value. Tested against the class it
exists to catch, on a real artifact, not only in its self-test.

It then caught a live tag inside its own documentation example in
InnerLoop.md within the hour. Third time a gate has failed on its own
pass's work.

What it does not close is stated rather than implied: 22 untagged literal
copies remain and are reported, not failed. Tagging is opt-in, a number
can legitimately recur, and a gate that fires on coincidence gets routed
around. Naming the uncovered surface beats claiming the class is closed.

InnerLoop single-source-of-fact moves from prose to executable — v1.3.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

facts.toml

@@ -0,0 +1,100 @@
+# GENERATED — do not edit. `make facts-gen` rewrites this file.
+#
+# The single source of fact for numbers that appear in more than
+# one artifact (InnerLoop v1.2). Every value here is produced by
+# the instrument named in its `by` field, on the current tree.
+# `make facts-check` fails if this file disagrees with the
+# instruments, or if a tagged artifact disagrees with this file.
+
+generated = "2026-07-31"
+pin = "fc76445"
+
+[am4a_loc]
+value = 246250
+text = "246,250"
+fmt = "{:,}"
+by = "tools/dep-weight.py"
+
+[am4a_target]
+value = 250000
+text = "250,000"
+fmt = "{:,}"
+by = "tools/dep-weight.py TARGETS"
+
+[am4b_loc]
+value = 317021
+text = "317,021"
+fmt = "{:,}"
+by = "tools/dep-weight.py"
+
+[am4b_target]
+value = 350000
+text = "350,000"
+fmt = "{:,}"
+by = "tools/dep-weight.py TARGETS"
+
+[gr_covered]
+value = 58
+text = "58"
+fmt = "{:,}"
+by = "tools/rule-coverage.py"
+
+[gr_linked]
+value = 49
+text = "49"
+fmt = "{:,}"
+by = "tools/rule-coverage.py"
+
+[gr_rules]
+value = 58
+text = "58"
+fmt = "{:,}"
+by = "tools/rule-coverage.py"
+
+[gr_scenarios]
+value = 21
+text = "21"
+fmt = "{:,}"
+by = "tools/rule-coverage.py"
+
+[pinned_main]
+value = 92.03371920000004
+text = "$92.03"
+fmt = "${:,.2f}"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_mechanical_cost]
+value = 33.3506319
+text = "$33.35"
+fmt = "${:,.2f}"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_mechanical_share]
+value = 36
+text = "36%"
+fmt = "{:d}%"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_mechanical_turns]
+value = 167
+text = "167"
+fmt = "{:,}"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_responses]
+value = 346
+text = "346"
+fmt = "{:,}"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_subagent]
+value = 1.1137235
+text = "$1.11"
+fmt = "${:,.2f}"
+by = "tools/cb-cost.py --pin fc76445"
+
+[pinned_total]
+value = 93.14744270000004
+text = "$93.15"
+fmt = "${:,.2f}"
+by = "tools/cb-cost.py --pin fc76445"