Amend ADR-0053: community default 2313 with keep-observed Group 3 controls 🟪

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

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

@@ -42,15 +42,27 @@ gap-log, and with them Part C stayed blocked:
    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.
+2. **Community heating (301/302) defaults to control 2313, keeping an
+   assessor-observed Group 3 control** (decided with Khalim, revising the
+   first-cut 2301). The control encodes two independent unknowns and the
+   default is chosen per axis:
+   - **Kit axis** (thermostat/TRVs): community schemes skew modern, and the
+     portfolio's own lodged community certs are overwhelmingly thermostatted
+     (modal control 2306; none lodge 2301) — so 2313 ("flat rate charging,
+     room thermostat and TRVs", temperature adjustment 0.0) concedes this
+     axis to the evidence.
+   - **Charging axis** (flat rate vs usage-linked): the billing arrangement
+     is scheme paperwork an override genuinely cannot see, so flat rate
+     (Table 4c(3) space **1.05**, DHW **1.05**) is retained — the
+     usage-linked credit (1.0/1.0) is never assumed.
+   - **Keep-observed**: when the cert already lodges a Group 3 control the
+     override is confirming a community system, not replacing one — the
+     assessor observed that control, and stamping any default over it
+     destroys real information (a usage-linked 2306 is worth ~1-2 SAP over
+     flat-rate). The overlay opts in via
+     `keep_existing_heat_network_control` (the control mirror of ADR-0035's
+     `keep_existing_off_peak_meter`); only a stale cross-family control (the
+     boiler-2110 / storage-2401 inheritances) is replaced by 2313.
 
 3. **An incomplete companion set now raises** (`ValueError`) instead of
    logging. Every archetype in `_MAIN_HEATING_CODES` resolves a complete
@@ -65,22 +77,30 @@ gap-log, and with them Part C stayed blocked:
 ## 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.
+- Community overrides converge on defensible controls with minimal score
+  churn. Live sample (portfolio 796, 12 properties): the ten dwellings with
+  assessor-observed Group 3 controls (2306/2307/2309) shift **±0.0** — their
+  observed controls survive the override — and only the two group-incoherent
+  dwellings (a Group-1 *boiler* zone control 2110 riding on a heat network)
+  move, **−1.0** each onto the 2313 default. Contrast the first-cut 2301
+  design, which shifted the whole sample 0 to −3.
 - 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.
+- **The maximally conservative community default (2301).** The first cut.
+  Rejected on evidence: no lodged community cert in the portfolio carries
+  2301, so it under-rates the typical (modern, thermostatted) scheme and
+  shifted the sampled cohort 0 to −3 SAP for no informational gain.
+- **A usage-linked community default (2306/2312/2314).** Rejected: credits a
+  billing arrangement the landlord never reported — the charging axis is the
+  one the override genuinely cannot observe, so it stays flat-rate.
+- **Stamping the default over an observed Group 3 control.** Rejected: the
+  ADR-0035 "always stamp" pattern exists to kill *stale* companions; an
+  in-group control on a confirmed community cert is observed data, and
+  overwriting it is information destruction, not coherence.
 - **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.