Record ADR-0053: companion taxonomy complete, incomplete set raises 🟪

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/adr/0053-heating-override-companion-taxonomy-complete-incomplete-set-raises.md

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+# The heating-override companion taxonomy is complete; an incomplete set now raises
+
+## Status
+
+accepted
+
+## Context
+
+[ADR-0048](0048-heating-override-forces-category-and-control-defers-fuel-and-meter.md)
+set the invariant — a system-replacing heating override emits a complete
+category + control companion set, never inheriting the replaced system's — and
+intended, once the taxonomy was covered, to "flip the log to a raise, so the
+coherence invariant is enforced" (#1444 Part C).
+[ADR-0050](0050-electric-underfloor-override-drags-category-8-and-conservative-group-7-control.md)
+(underfloor) and
+[ADR-0052](0052-electric-boiler-and-cpsu-overrides-drag-category-2-and-conservative-group-1-control.md)
+(electric boilers) filled two families. Two archetype families remained on the
+gap-log, and with them Part C stayed blocked:
+
+- **"Air source heat pump" (SAP 211)** — category 4 already forced, control
+  `None` (Table 4e Group 2 unmapped). No live overrides today (census across
+  all portfolios: 0), so this is taxonomy completion, not a live defect.
+- **"Community heating, boilers" / "…, CHP and boilers" (301/302)** — category
+  6 already forced, control `None` (Group 3 unmapped). **2,220 live
+  overrides** — the largest population on the log. The inherited control is
+  doubly load-bearing for heat networks: it feeds the Table 4e temperature
+  adjustment *and* the SAP 10.2 Table 4c(3) charging factors (worksheet
+  (305)/(305a)).
+
+## Decision
+
+1. **Wet heat pumps (Table 4a 211-224) drag control 2201** — Table 4e Group 2
+   "no time or thermostatic control of room temperature", **+0.3 °C**, the
+   largest Group 2 adjustment: the conservative in-group default (the heat-pump
+   mirror of storage 2401 / room-heater 2601 / underfloor 2701 / boiler 2101).
+   Warm-air heat pumps (521-527) are deliberately left unmapped — no archetype
+   reaches them, and the raise below is the guard that a future warm-air
+   archetype cannot land without choosing its Group 5 control.
+
+   This is the *existing-system* fill policy: the ASHP **Measure** overlay
+   installs 2210 (time-and-temperature zone control) because a measure designs
+   a modern end-state (ADR-0024); a landlord override describes an existing
+   pump whose control was never observed, so the conservative default applies.
+
+2. **Community heating (301/302) drags control 2301** — Table 4e Group 3
+   "flat rate charging, no thermostatic control of room temperature". It is
+   the never-over-crediting default on **both** axes the control drives: the
+   largest Group 3 temperature adjustment (**+0.3 °C**, tied with 2302) and
+   the worst Table 4c(3) charging factors (space **1.10**, DHW **1.05** — an
+   unobserved charging arrangement is never assumed to be usage-linked).
+   As with every forced companion (ADR-0035/0048 pattern), this overwrites a
+   better control lodged for the replaced system: the override asserts the
+   system afresh and synthesis owns coherence.
+
+3. **An incomplete companion set now raises** (`ValueError`) instead of
+   logging. Every archetype in `_MAIN_HEATING_CODES` resolves a complete
+   category + control (gas boilers via their dedicated overlay; all others via
+   `_category_for`/`_control_for`), so the log-and-continue mitigation has no
+   remaining population — and a silent log was only ever a stop-gap
+   (ADR-0048: "the intended end-state is to fill each archetype's
+   category/control … and then flip the log to a raise"). A future archetype
+   added without companions now fails loudly at overlay time rather than
+   shipping a silently-incoherent cert.
+
+## Consequences
+
+- The companion-gap error log is gone; #1444 closes.
+- Community overrides re-model against the conservative 2301: dwellings whose
+  replaced-system control was inherited converge on one defensible assumption.
+  Live sample (portfolio 796, 12 properties): baseline shifts of **0 to −3
+  SAP** (typically −1 to −2). The inherited controls were unobserved
+  usage-linked credits (2306/2307/2309) or outright group-incoherent — two
+  dwellings carried a Group-1 *boiler* zone control (2110) on a heat network —
+  so the shift removes credit that was never evidenced.
+- Adding a heating archetype now *requires* choosing its category + control
+  (or extending the family sets) — the raise turns the ADR-0048 checklist into
+  an enforced contract.
+
+### Alternatives rejected
+
+- **A zero-adjustment / usage-linked community default (2307+).** Rejected:
+  credits a charging arrangement and thermostat the landlord never reported;
+  the conservative default is the established pattern.
+- **Keep log-and-continue indefinitely.** Rejected: the log was the interim
+  mitigation while the taxonomy was incomplete; leaving it means the next
+  archetype ships the ADR-0048 inheritance bug silently again.
+- **Raise on warm-air heat-pump codes' missing control now.** Not applicable —
+  no archetype maps to 521-527; the raise fires exactly when one is added
+  without its Group 5 control, which is the point.