fix(documents): tell the summary outcomes apart instead of promising one forever

A summary is enqueued only when a document is uploaded while automatic
reading is already on, and nothing backfills the ones uploaded before
that. The detail view read a null summary as 'being generated' and said
so permanently, while the manual action row was hidden precisely when
automatic reading was on - so the promise could never be met and the
repair was out of reach.

Record what actually happened. Seven outcomes previously collapsed into
the same null: never enqueued, opted out, no vision provider, spent
budget, consent refused, unreadable file, provider error, plus the
withhold. Each now names itself and offers a manual generation, and what
that produces is kept.

The withhold rule is unchanged - refused prose is still never shown or
stored - but recording the refusal as a state makes it re-attemptable
instead of a permanent dead end.

Also removes the read-by-AI footer.

CHANGELOG.md

@@ -20,8 +20,16 @@
 - **The "read the full briefing" link is gone from Today.** Tapping the
   health-score ring already opens the same page.
 - **The close button on a document sits flush with the edge again.**
+- **A document no longer says its summary is being generated forever.**
+  Summaries are only started when a document is uploaded while automatic
+  reading is on — there is no catch-up for documents you already had, so
+  the view promised a summary that was never coming, and hid the button
+  that would have made one. It now says what actually happened — not
+  attempted, unavailable, or held back — and offers to generate one in
+  every case. A summary you generate that way is kept.
+- **Removed the "read by AI" note** at the bottom of a document.
 
-No breaking changes.
+One migration (0254). No breaking changes.
 
 ## [1.30.28] — 2026-07-19