Merge branch 'mantra' into claude/marmot-direct-message-type-7a0473

Twenty-two commits had landed on mantra since this branch left it, several
of them in the same files. Merged this way round so mantra stayed untouched
until the result compiled and its tests passed.

The migration had to be renumbered, and this is the conflict that mattered.
mantra is at database version 7 and already has its own 5.json -- for
MarmotInnerEvent.payloadEventId, nothing to do with direct messages. This
branch had also written a 5.json, for a different schema. Resolved by
restoring mantra's 5.json untouched and moving the direct message columns
to an AutoMigration(7, 8) with a regenerated 8.json. Taking either 5.json
over the other would have left every device validating a migration chain
against a schema it was never built from; keeping version = 5 would have
made a v7 install refuse to open at all.

The regenerated 8.json is two ADD COLUMNs and nothing else, same as before.

fromGroupEventResult was restructured on mantra: the kind switch moved into
applyInnerEvent, and a SubmissionEvent envelope now wraps nip30303 payloads.
Took that structure and re-applied the direct message branch ahead of it
rather than inside it -- a gift wrap is not a nip30303 payload to apply, and
what happens to it depends only on whether this device's key opens it, so it
does not belong in a function about applying submissions.

The isUserMessage fix was re-applied to the eight call sites mantra's
version has, up from the six it had here.

ChatMessageListViewModel and ChatRoomMessagingScreen took mantra's versions
with the composer state, the two renderings and the reply action layered
back on.

docs/README.md keeps both new rows and mantra's closing note about the
skipped-keys document.

108 tests pass, up from 50 here and 83 on mantra.

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

docs/README.md

@@ -10,5 +10,8 @@ silent, or a decision that looked arbitrary and was not.
 | [shared-key-derivation.md](./shared-key-derivation.md) | deriving further keys from the group's threshold key with FROST tweaks — why not BIP32, why no chain code, and the one rule that must not be broken |
 | [marmot-membership.md](./marmot-membership.md) | how members join an MLS group, and the epoch race that makes a missing member look like a successful invite |
 | [marmot-direct-messages.md](./marmot-direct-messages.md) | a one-to-one message inside a group as a stock NIP-59 gift wrap — what its MIP-03 carve-out costs, why the sender cannot read their own, and the one query that would broadcast it |
+| [mls-skipped-keys.md](./mls-skipped-keys.md) | why a group event that arrives a moment late is dropped for good, which flows trigger it, the quartz fix, and the partial mitigation in this app |
 
 Start with the ceremony if you are new to this area; everything else here assumes it.
+Read the skipped-keys note before debugging any "the other device never got it"
+report — it is silent, and it looks like every other kind of delivery failure.