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## Summary
When two identities share a display name, Buzz mobile shows the same
label for both. A reader cannot tell a person from an agent, or one
person's agent from another's. For example, a channel can show three
agents and one human all named "murderbot".
This PR adds the naming rules that fix this, without changing any screen
yet. It ports the contextual identity-name contract (v1) from the
desktop app to Dart. Given the identities shown together, the resolver
gives each public key a distinct label:
- A human keeps the plain name. Agents that share it get a qualifier.
- The viewer's own agents are named before other people's agents.
- An agent is qualified by its owner's name first ("Wes's Honey"). A
short public-key suffix is added only if that is still ambiguous
("baxen's murderbot · xa8v").
It also adds two providers that screens will use:
- `channelIdentityNamesProvider` compares names against a channel's
members, plus any referenced non-member such as an old author or an
outside mention.
- `watchIdentityNames` compares a set of identities shown together
outside a channel, and loads their profiles.
The next PRs in this stack connect these to the screens.
Part 1 of 3: #7894 (resolver) → #7895 (conversations) → #7896 (lists,
Search, Pulse).
### Related issue
Related to #2910 (default "Fizz" agents from different users collide in
one channel).
### Testing
- The contract's 31 portable fixture cases run against the production
resolver. The fixture file is copied unchanged from the contract, so
reviewers can skip it.
- Unit tests cover owner and suffix qualification, the viewer's own
identities, and invalid public keys.
- Provider tests check that a channel keeps its names while its roster
reloads, that an offline cached bot still counts as an agent, and that
changing relay or account never shows the old roster.
- `flutter analyze` is clean.
No UI change, so there are no screenshots.
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Signed-off-by: Logan Johnson <loganj@squareup.com>
Co-authored-by: Larry <627498bd4bd1f281a16431e3c6cce3b5c25b6692798c78672298aefbf2f8f8b5@buzz.block.builderlab.xyz>