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/DATA-MODEL.md

@@ -829,6 +829,61 @@ media_asset:
 
 Potential metadata includes prompt, seed, model, workflow, dimensions, duration, character references, and source turn range.
 
+## 28A. Media Extension Points (M10, as implemented)
+
+M10 implemented the seams the two sections above describe, and the implementation
+is mostly an account of what it did **not** build.
+
+```text
+visual_profiles             the one thing M10 persists
+  id, adventure_id          campaign-scoped; no branch coordinate, deliberately
+  entity_key                the M5 narrative-state key: "mara", "the_office"
+  descriptors               open map of trait -> value
+  features                  list of distinctive visible things
+  style_notes               free text about how it should be rendered
+  created_at, updated_at
+  UNIQUE (adventure_id, entity_key)
+```
+
+No `scenes` table. No `media_jobs` table. No `media_assets` table.
+
+**The scene snapshot of §20 already exists**, and has since M5. It is
+`narrative_state["scene"]` — `summary`, `location`, `present[]`, and the
+`at: {branch_id, depth}` coordinate that says where it was written. It is
+produced by the validated `set_scene` event, snapshotted per position in
+`actions.narrative_state_after`, restored by the head move on every Undo, Redo,
+Retry and Save Point restore, and carried in the v3 bundle. Building a second
+scene record beside it would have been a duplicate representation of the same
+fact with its own lineage rules to get wrong — and the lineage rules are the hard
+part, which is exactly why the answer is to reuse the one that already works.
+
+So the **Scene Packet** (`app/media/packet.py`) is *derived on read* and stored
+nowhere. Its identity is `c<adventure>:b<branch>:<start>-<end>`, computed from
+the campaign and the position rather than allocated, so the same position yields
+the same id in any process and after any restart without a row to keep in step.
+
+`media_job` and `media_asset` (§27, §28) remain **unbuilt**. M10 defines their
+contracts as `typing.Protocol` structural types in `app/media/providers.py` —
+`MediaProvider`, `SpeechProvider`, `TranscriptionProvider`, and the
+`MediaRequest` / `MediaResult` / `DraftTranscription` shapes — with an empty
+registry. A queue with no producer and no consumer would be speculative
+architecture, and this codebase has already declined that once: M6's
+`derived_status` carries the note "not a job queue".
+
+**Why a visual profile has no branch coordinate.** Every other derived record in
+the schema carries `(branch_id, depth)` because it describes a *moment*. A
+profile describes none: a character does not change appearance because the story
+forked. Making it per-position would have hidden a reader's cast from them the
+moment they diverged, and would have put a descriptor document into every
+per-position snapshot — measured at 245 copies of 367 bytes in a 120-turn
+campaign, to say something that never varies (`tools/m10_media_cost.py`).
+
+**A profile is not a fact.** Nothing here is state the story established.
+Writing one cannot change `narrative_state`, and the guarantee is structural
+rather than remembered: nothing in `app/media/` imports the code that writes it.
+The reverse direction is the same rule seen from the other side — a depiction
+never becomes canon (`MEDIA-EXTENSION-CONTRACT.md` §35, §37).
+
 ## 29. Export Package
 
 A campaign export should be capable of preserving: