development: code relying on another component cites its source; stage 2c: the heuristics review

Owner, 2026-10-14: "нам нужно полное ревью кода на предмет всей этой
эвристики. Её не должно там, где можно посмотреть код и ответить точно и
однозначно", and "в коде таких наших блоков должно быть обоснование со
ссылкой на код компонента".

- development.md § Code that relies on another component's behaviour: the
  rule, with the form of the comment (component, the image's version, file,
  function; or a document's URL and section; or "measured on the stand,
  date" said as such), and fixtures saying whether they were seen or
  composed.
- Audit stage 2c: the line "what was taken on trust" becomes the heuristics
  review - an inventory over the whole tree written down as
  docs/assumptions-2026-10-14.md, then each answered from the source of the
  version the image runs, the comment added, the code fixed where it
  contradicts. Plan still 66 lines.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/development.md

@@ -215,6 +215,30 @@ Plex [OFL.txt](../internal/web/view/static/OFL.txt) under
 `/usr/share/doc/selfpost/`. The panel serves the AGPL text at `/license` and
 the OFL text at `/static/OFL.txt`.
 
+### Code that relies on another component's behaviour
+
+The owner's rule (2026-10-14): what another program does is read in its
+documentation or its source - never guessed. SelfPost reads Postfix's log
+lines and reply codes, feeds OpenDKIM's tables, parses `postqueue`,
+`postconf`, `supervisorctl` and `db_dump` output, talks the milter protocol
+through go-milter, relies on SQLite's locking, on logrotate's and Docker's
+behaviour. Every block of code that does so carries a comment that says
+what it relies on and where that is written, for the version the image runs
+(the Debian bookworm package, not upstream's head):
+
+```go
+// Postfix 3.7.11, src/smtpd/smtpd_check.c, check_sender_login():
+// the SASL login is compared with the sender map's owners by strcasecmp.
+```
+
+A document instead of source: its URL and section. Where neither answers the
+question, the comment says so and what was measured instead - "measured on
+the e2e stand, 2026-10-14: ..." - and a measurement is never written as if
+it were read. A test fixture copied from a real log says where and when it
+was seen; one composed by hand says that it was composed. The heuristics
+review of 2026-10-14 (audit-2026-10-12, stage 2c) brought the code that
+existed then up to this rule.
+
 ---
 
 ## Building binaries and the image