M9: a campaign you can actually get back

A campaign could already be exported and imported. What could not survive the
trip was everything that explains it: the state events behind the authoritative
document, the prompt each turn was actually given, the passages it was shown,
the summaries that carry long-story continuity, and which take belonged to which
turn. An imported campaign could be read and could no longer say why it was what
it was — and a manual correction, the one state change no narration explains,
was indistinguishable from something the story had established.

The bundle is now `ai-dnd-adventure-v3`, and the version is the design rather
than a side effect. Everything added here could have been another optional key,
the way persona, Save Points, narrative state and imported knowledge each were.
That mechanism stops working at exactly this addition: a v2 file with no prompt
provenance is ambiguous between "written before M9" and "written by M9 from a
campaign that has none", and those are different facts about a campaign. A
version number is how a recovery file states what it was capable of recording.
v1 and v2 still import, and every seam from pre-active-head onward is tested for
the rule that an older file is never reinterpreted under a newer assumption.

Two categories became three. "Chosen travels, derived is recomputed" was enough
until stored prompts had to be decided: they are derived, and they must travel
anyway. The test that separates evidence from cache is not "could this be
recomputed" but "would a recomputation answer the same question" — a rebuilt
search index answers the same question, a rebuilt prompt says what the turn
would be told *now*, which is the opposite of what the inspector is for.

Also here: a real SQLite backup, through the online backup API rather than a
file copy, taken while the application is running and verified before it is
kept; story cards settled as compatibility-only legacy data and taken out of the
narrator's prompt, because they were the untracked path around knowledge
authority that IMPORTED-KNOWLEDGE-DESIGN §73 already forbade; and no schema
change at all, proved against a database M8's own code wrote.

Three defects, found by running the milestone's own tests rather than by reading
them. Deleting a campaign leaked its FTS index rows, and SQLite then handed the
freed ids to the next source imported into any campaign, which failed with an
integrity error that Reindex could not repair — both ends are closed, and a
database already carrying the damage now repairs itself. An imported node with
no state snapshot was being stamped with the campaign's head state, so an Undo
to turn 2 showed what the story knew at turn 20. And the snapshot relink did not
persist at all, because it mutated a dict in place on a column SQLAlchemy tracks
by assignment: it looked correct in memory and wrote the wrong ids to disk.

Carrying per-turn prompts looked like it would halve the length of campaign that
can be restored. Measured — and after compressing them inside the file —
everything M9 added costs 12% of it: the import ceiling moves from about 318
turns to about 279, against a 100-turn certification target. The dominant cost
is not M9's at all. The per-position narrative state document is 74% of a
bundle, and v2 already carried it.

Backend 1,102 passed / 14 skipped / 0 failed. Frontend 145 passed. Lint,
production build and Docker build clean. Verified across two server processes
with two data directories, and in a real browser against a real narrator.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qyn3oRd4D6pi72nKBG725B

planning/BROWSER-UX-SPEC.md

@@ -128,6 +128,35 @@ The current endpoint should be clear.
 
 The input box always continues from the currently active story head.
 
+### 8A. The reader must be able to tell where they are (recorded 2026-09-07)
+
+A hands-on session against accepted M8 found the sentence above **too weak to
+hold the behaviour it names**. Undo worked correctly, the input box did continue
+from the active head — so both statements above were satisfied — and the reader
+still could not tell which point in the story they had moved to.
+
+The requirement, stated so that a working implementation cannot satisfy it while
+a reader is lost:
+
+> After Undo, Redo, a Save Point restore, an edit to an earlier turn, or any
+> other movement of the active story position, the reader should be able to
+> identify **where they now are in the visible story** — and, where it matters,
+> whether later story remains available ahead of them.
+
+Two constraints on any solution:
+
+- **No implementation terminology.** `branch`, `fork`, `node`, `head` and
+  `depth` stay off the reader-facing surface (§38), which is what makes this a
+  presentation problem rather than a labelling one.
+- **It must be observable**, not merely inferable from the transcript scrolling,
+  so that a release test can decide it.
+
+**No wording is prescribed here, and none is ratified.** A lightweight named
+position — `Moment 8` becoming `Moment 7` after an Undo, optionally noting that
+later story is available — is one candidate among others. Ownership is M11
+release polish; `V1-ACCEPTANCE-TESTS.md` §P1 records what must be settled before
+this can become an acceptance test.
+
 ## 9. User Turn Presentation
 
 User messages should support: