feat(android): the write transport, and an error that says why

TSyncClient.Put publishes a container to the Gitea contents API: token header,
JSON envelope with the file base64 inside, sha omitted rather than empty when
creating, branch omitted so the repo default is used. 409 becomes its own
status, ssConflict, because it means re-read and re-apply rather than retry.

The first PUT is where a mistake costs data, so the probe writes to
write-test.json rather than the vault. Same repository, same token, same
envelope, same concurrency check - and the vault is never at stake. Reachable
from a debug-only button; the page asks Delphi whether to show it.

Two mistakes of mine on the way, both about replacing information with a guess:

- the probe did not push the config first, unlike Sync, so a token that had
  just been pasted had not reached Delphi and the 403 blamed the wrong thing.
- 401 and 403 were rewritten as "token lacks write access", discarding Gitea's
  body. That is an interpretation, not an observation: the same code covers a
  read-only repository, a protected branch, a token from another account. The
  body says which - here, plainly, "token scope=read:repository".

Also recorded: the sha comparison now short-circuits (304 where it used to
decrypt), so the difference was case or whitespace, absorbed by SameText on
trimmed values. The offending character itself was never seen.

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

android-client/PLAN.md

@@ -170,7 +170,7 @@ tentée d'abord : MSBuild l'ignore, comme il ignore toutes les autres ici.
 régénération de `web.res` — l'oublier embarque la page d'avant l'édition, et le
 symptôme se lit alors comme un bug applicatif.
 
-## 1 quater. OUVERT — la comparaison de sha ne se declenche pas
+## 1 quater. ~~La comparaison de sha ne se declenche pas~~ — RESOLU le 2026-08-17
 
 Mesure sur appareil, deux ouvertures successives du cache :