M10: the seam for media, and no media

The media extension contract asks for a scene snapshot a future image or video
provider could be handed: location, who is present, what they hold, what must
stay true, and where in the story it sits. Building one was the milestone's
obvious first task, and it was the wrong one. That snapshot has existed since
M5. `narrative_state["scene"]` holds the summary, the location, the cast and the
coordinate it was written at; a validated `set_scene` event writes it, every
position snapshots it, and every head move restores it. It survives Undo, Redo,
Retry, divergence, Save Point restore and a process restart because it is the
authoritative state rather than a copy of it.

So there is no scenes table here. A second scene store would have been a second
answer to "where is the story now", with its own lineage rules to get wrong —
and the lineage rules are the expensive part, which is the argument for reusing
the ones that already work rather than against it. The Scene Packet is derived
on read, and its identity is computed from the campaign and the position rather
than allocated: the same position yields the same id in another process, after a
restart, and after the packet is thrown away and rebuilt, with no row to keep in
step. That is the part of a future media_assets table that would be expensive to
retrofit, so it is fixed now even though the table is not built.

One table, then: visual_profiles, the only thing the contract's scene list asks
for that nothing already stored. Campaign-scoped and not per-position, because a
character does not change appearance when the story forks — a reader who
diverged would otherwise lose their cast, and the same descriptors would land in
every per-position snapshot, measured at 245 copies of 367 bytes in a 120-turn
campaign to say something that never varies. Keyed by the M5 entity key rather
than a new identity namespace, and one table for characters, locations and items
alike, because a location is an entity with a type and splitting them would
reintroduce the genre shape M5 spent a milestone removing.

What the packet leaves out is the more interesting half. Not the transcript, and
not imported knowledge — none of it, not merely the sources marked hidden. The
rule is what the story established at this position, not everything the narrator
was told, and drawing it by class is what makes it hold for a secret nobody
thought to mark. A hidden Canon source proves it, with a positive control
showing the narrator did receive the sentinel the packet does not carry. Once a
validated event puts the observer in the room, the observer is in the packet:
that is no longer narrator-only knowledge, and a packet that hid it would be
hiding the story from itself.

The providers are contracts and nothing else. Protocols for image, video, audio,
speech and transcription, an empty registry, no adapter, no dependency, no
socket, and no media setting to point anywhere — a setting that exists can be
pointed at a cloud by mistake. A future provider endpoint must be loopback,
stricter than narration's trusted-LAN allowance, because a picture of a scene
carries the scene with it. Transcription returns an editable draft with no
commit method, so STT structurally cannot bypass the authoritative path.

Nothing here can write the story. Not by convention: no module under media/
imports the code that writes state, no media event type exists in the state
vocabulary, and every test in the authority suite compares the authoritative
document byte for byte either side of a media operation — including one where a
provider insists Alice is in a red coat in a corridor, and the campaign goes on
disagreeing.

One defect, found by the milestone's own tests. M10 first added a migration
creating an index that create_all already builds from the column, so an upgraded
database ended up with two indexes and a fresh install with one. Comparing the
two schemas is what caught it; neither database examined alone would have. The
migration is gone rather than renamed, and the right number of migrations for a
new table whose indexes are declared on its columns is zero.

Backend 1,191 passed / 14 skipped / 0 failed, 89 of them M10's. Frontend 145
passed. Lint, production build and Docker build clean. No frontend file changed:
M10 adds no reader-facing surface, and ordinary play — turns, state, memory,
knowledge, Undo, Redo, Retry, Save Point restore, restart — runs with no media
configuration, no warning, no connection attempt and no media row written.

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

planning/BUILD-MILESTONES.md

@@ -1345,6 +1345,67 @@ Do not implement:
 
 Future media providers can be added through defined local interfaces without redesigning core story authority/history.
 
+## Status: COMPLETE — 2026-09-07, pending independent review
+
+Implemented on `m10-media-hooks` from the signed M9 commit `44edece`.
+`planning/reports/M10-IMPLEMENTATION-REPORT.md` is the implementer's account,
+written for a reviewer.
+
+**The finding that shaped the milestone: the scene snapshot already existed.**
+
+The media contract's §5 asks for a persisted or derived scene snapshot, and M5
+built one three milestones ago. `narrative_state["scene"]` holds the summary, the
+location, who is present and the `(branch_id, depth)` coordinate; it is written
+by a validated `set_scene` event, snapshotted per position, and restored on every
+head move. That was verified with a probe — a campaign played, diverged, undone
+and exported — rather than taken from M9's report.
+
+So M10 built **no scenes table**, and the Scene Packet is derived on read with a
+computed identity (`c<adventure>:b<branch>:<start>-<end>`) rather than an
+allocated one. A second scene store would have been a duplicate representation of
+the same fact, with its own lineage rules to get wrong; the lineage rules are the
+hard part, which is precisely the argument for reusing the ones that already
+work.
+
+**What it delivered:**
+
+- **One table, `visual_profiles`** — the only field in the contract's scene list
+  that nothing already stored. Campaign-scoped rather than per-position, because
+  a character does not change appearance when the story forks, and because
+  per-position profiles would have cost 245 copies of the same 367 bytes in a
+  120-turn campaign to say something that never varies.
+- **A scene packet built on read**, excluding the raw transcript, all imported
+  knowledge, memories and summaries. Excluding imported knowledge *as a class* is
+  what keeps a hidden Canon source out of a future depiction without a filter
+  anyone has to remember to extend.
+- **Provider contracts as `typing.Protocol` structural types**, with an empty
+  registry, no adapter, and no dependency added. Nothing imports a media library
+  because none is installed.
+- **The STT asymmetry in the type**: a `DraftTranscription` is editable and has
+  no commit method, so a transcriber structurally cannot bypass the authoritative
+  commit path.
+- **A stricter endpoint policy than narration uses** — loopback only, reusing
+  `endpoints.py`'s resolved-address check rather than trusting a hostname. No
+  media configuration setting exists, because one that exists can be pointed at a
+  cloud by mistake.
+- **Profiles travel in the bundle** with no format bump. M9's own semantic test
+  decides it: an absent `visualProfiles` key is unambiguous, because a campaign
+  with no profiles is the ordinary case. Older v3 files still import.
+
+**A defect found by the milestone's own tests, and fixed here:**
+
+- **A redundant index migration made two databases disagree.** M10 first shipped
+  migration 93 creating `ix_visual_profiles_adventure`. `create_all` already
+  builds `ix_visual_profiles_adventure_id` from the column's `index=True`, on
+  fresh installs and existing databases alike — so an *upgraded* database ended
+  up with both indexes and a fresh one with only the second. The comparison of a
+  fresh schema against an upgraded schema is what caught it. **M10 adds no
+  migration at all**; `LATEST_VERSION` stays 92.
+
+**Carry-forward, unchanged by this milestone:** the four post-M8 playtest
+findings recorded above (browser title, post-Undo orientation, narration length,
+character identity) remain **M11's**. M10 neither implemented nor tested them.
+
 ---
 
 # M11 — v1 Security, Long-Run, and Release Validation