Merge release/1.0 (FCST-06) into TARIFF-08

One conflict, in CHANGELOG.md's `## Unreleased` block, exactly as expected
from two branches landing beside each other: both `_this branch_` table rows
and both sections are kept, FCST-06's first. Nothing else conflicted -
FCST-06's `test_price_history.py` section 5d and this branch's columnar
`feed_body()` merged cleanly - and all 29 test files are green on the result.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/DOCS.md

@@ -1509,10 +1509,20 @@ first fill is possible the day after the first refresh.
 
 The same applies to a file that is *partly* broken: a day record this build
 cannot read is dropped, the row says how many were dropped and why, and the rest
-of the file still loads. And where there is no `/data` at all the store records
-**nothing** — not even in memory. An in-memory yesterday would answer for one
-run and vanish on the next restart, which is a cache that forgets without saying
-so; `unavailable` and *no prices carried* are the honest pair.
+of the file still loads. And a store that **cannot persist records nothing** —
+not even in memory. That covers a missing `/data`, and it also covers a `/data`
+that is there and cannot be **written**: a full volume, a read-only remount. An
+in-memory yesterday would answer for one run and vanish on the next restart,
+which is a cache that forgets without saying so; the row naming the reason and
+*no prices carried* are the honest pair.
+
+⚠️ **What a failed write does not do is throw away what is already in the
+file.** A volume that fills at 14:00 leaves the yesterday written at 13:30 still
+answering, because that record survives a restart — the store stops *adding* to
+it, nothing more. And it never stops the add-on: a write that cannot complete is
+logged and reported on the status row, never raised. A cache that cannot answer
+is not allowed to be a controller that cannot regulate, and that applies to the
+volume being full exactly as it applies to the volume being absent.
 
 **Injection is priced separately** (`export_price_eur_kwh`). In Belgium it is
 often near zero, which by itself strongly favours self-consumption over export.