fix(mobile): show shared chats under Solo - #9348

## Summary

Fix for a blocking review finding on #9348 ([review
thread](buzz://message?channel=95213a25-483a-458b-9bc3-71891fa5aef6&id=8ad087852227b50d614760eb4778734e306faf70df77e0ecd16cb5816b865bbc)).

**Wait, what?** #9348 removes shared and agent-created Solo chats from
Team as soon as the channel list loads, but the Solo list and its unread
badges waited for the separate encrypted filing record. With no usable
record (fresh install or sign-in before it arrives, offline without a Me
cache), those chats were listed and badged nowhere. Before #9348 they
were reachable under Team.

**Now:** Solo builds its chat list and unread set from the channel list
alone. While the filing record loads or fails, its spinner or "Try
again" shows as the first item above an unfiled "Chats" list, with no
project sections and no "No chats yet" empty state. Legacy (pre-label)
chats and project filing join when the record arrives. New chat / New
project stay disabled until then, and nothing is written from the
unavailable state.

**Nothing gets worse:** with the record loaded, the page renders exactly
as before. The only visible change is in the loading/error state, where
the status moves from replacing the list to sitting above it.

### Testing

Added tests:
- `me_page_test`: Home with an ordinary chat and a labelled shared chat,
filing record failing or still loading. The shared chat is listed under
Solo, the ordinary one under Team, and the status (retry or spinner) is
shown. Both fail on #9348's head.
- `me_unread_test`: a labelled shared chat with a new message is counted
before the record loads, and a legacy id joins once it arrives. Fails on
#9348's head.

The existing "unavailable preferences show retry instead of empty state"
test still passes. Full mobile suite and `mobile-check` pass locally.

Signed-off-by: Tom Brow <[email protected]>
Co-authored-by: Tom Brow <[email protected]>
Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@buzz.block.builderlab.xyz>

Co-authored-by: mboston.Engineer <932d3b6ebea6cc83e091551ae46d1c7e7f8f7d0fa8e9cef5e6facc8544af413b@buzz.block.builderlab.xyz>

* origin/main:
  fix(mobile): require Builderlab consent for existing identities (#8823)
  feat(mobile): use HTTP/2 on iOS through app-wide URLSessions (#8897)
  fix(relay): publish a git push only when refs changed; check the protocol by refinement (#9425)
  fix(mobile): show shared chats under Solo (#9348)
  chore(release): release Buzz Desktop version 0.5.29 (#9456)
  feat(mobile): render messages with gpt_markdown 1.3.4 plusparse (#8945)
  fix(acp): bound observer retention by bytes (#7987) (#9436)
  Tune release codegen for faster/smaller binaries (#9434)
  feat(desktop): add dismissible banner pointing to the new buzz app (#9379)
  fix(mobile): keep publishing presence while the app is open (#9441)
  feat(mobile): share into Buzz from the iOS share sheet (#9433)
  fix(mobile): qualify every namesake mention and keep authored mention casing (#9325)
  fix(mobile): match browser GIF timing in the iOS reaction sheet (#9437)
  fix(mobile): play short-delay animation frames at browser speed (#9432)
  buzz-search: read profile names without the profile_name_fields function (#9397)
  buzz-db: build the community deletion lock key in Rust (#9396)
  fix(cli): pair for the active community, skip stopped desktops, accept a bare relay host (#9417)
  test(mobile): run push tests without a gateway dart-define (#9423)
  fix(mobile): never pop Home when archiving from channel settings (#9387)
  perf(acp): reduce observer CPU and lock overhead (#9381)

Signed-off-by: Matthew Boston <[email protected]>

…count-backfill

Co-authored-by: mboston.Engineer <932d3b6ebea6cc83e091551ae46d1c7e7f8f7d0fa8e9cef5e6facc8544af413b@buzz.block.builderlab.xyz>

* bostonaholic--agent-reply-count:
  fix(mobile): require Builderlab consent for existing identities (#8823)
  feat(mobile): use HTTP/2 on iOS through app-wide URLSessions (#8897)
  fix(relay): publish a git push only when refs changed; check the protocol by refinement (#9425)
  fix(mobile): show shared chats under Solo (#9348)
  chore(release): release Buzz Desktop version 0.5.29 (#9456)
  feat(mobile): render messages with gpt_markdown 1.3.4 plusparse (#8945)
  fix(acp): bound observer retention by bytes (#7987) (#9436)
  Tune release codegen for faster/smaller binaries (#9434)
  feat(desktop): add dismissible banner pointing to the new buzz app (#9379)
  fix(mobile): keep publishing presence while the app is open (#9441)
  feat(mobile): share into Buzz from the iOS share sheet (#9433)
  fix(mobile): qualify every namesake mention and keep authored mention casing (#9325)
  fix(mobile): match browser GIF timing in the iOS reaction sheet (#9437)
  fix(mobile): play short-delay animation frames at browser speed (#9432)
  buzz-search: read profile names without the profile_name_fields function (#9397)
  buzz-db: build the community deletion lock key in Rust (#9396)
  fix(cli): pair for the active community, skip stopped desktops, accept a bare relay host (#9417)
  test(mobile): run push tests without a gateway dart-define (#9423)
  fix(mobile): never pop Home when archiving from channel settings (#9387)
  perf(acp): reduce observer CPU and lock overhead (#9381)

Signed-off-by: Matthew Boston <[email protected]>