NEXUS-4029: Preserve semantic chips in the core composer - #2303

…a channel (#2512)

## TL;DR

Adds `conversation.ui.Conversation`, a public host-owned scope that lets
a plugin's own `ui.Message` rows and `ui.Composer` for one channel get
native Edit, confirmed Delete with recovery and retry, and host media
review. Mounting it never marks anything read, follows a thread or
enters the channel visit. Cross-channel overview cards need this; today
a bare `ui.Message` row has neither Edit nor Delete, and `ui.Thread`
always visits.

Fixes NEXUS-4193

## How it works

`ui.Conversation({ session, scope, channelId, channelName?, threadId?,
children(interactions) })` renders the existing `ConversationChannel` in
its host-dialog, non-visiting mode (`host` plus `active={false}`). Inbox
Drafts already uses this mode internally. Inside it:

- `MessageManagement` supplies the row menu's Edit/Delete under the
existing permission checks, the delete confirmation and the
failed/unconfirmed recovery notice.
- `MessageEditScope` makes Edit target the `ui.Composer` in the same
scope. A scope without a composer offers no Edit, as in other previews.
- `ConversationHost` owns media review and panel overlays, focus return,
and the existing stale-session guard (nothing opens once the relay
snapshot is no longer this ready session).

`children` receives the host's `onOpenLink`, `canOpenLink` and
`onOpenMediaReview` to pass to the rows. `EmbeddedThread` and the new
scope now share one `HostedChannel` wrapper, so `ui.Thread` behavior is
unchanged. No changes to `MessageManagement`, `ConversationHost`,
`MessageComposer` or `contracts.ts`.

## Evidence

`src/features/conversation/EmbeddedConversation.test.tsx` mounts two
fictional channel cards (real relay session, real `ui.Message` rows and
`ui.Composer` from `ConversationService`; only `MediaReviewViewer` is
reduced, since it has its own suites). It covers:

- the same rows without the scope have no Edit/Delete; inside it, each
card offers both
- mount, background presentation, re-present and unmount never call
`enterChannel`, `leaveChannel`, `follow`, `markMessageRead`,
`markChannelRead` or the roster's `profiles.reserve`, and publish
nothing
- Edit fills only that card's composer and publishes a kind-40003 edit
tagged with that card's channel. The other card's message is untouched.
- Delete: cancel publishes nothing; confirm publishes kind 5; a relay
rejection shows the recovery notice in that card only; Retry resends the
same event id and the row goes away
- media review opens with the card's channel and message, and stops
opening after the session stops being ready

Fail-then-pass: with `active={false}` removed from the scope, all 4
tests fail (`enterChannel` and `profiles.reserve` are called). The scope
restored, all pass.

The packed `@buzz/author` consumer fixture
(`tests/fixtures/conversation-consumer`) now renders its rows and
composer inside `ui.Conversation` and passes `interactions.onOpenLink`
to its rows. So the generated declarations must export the new component
and its `children(interactions)` type, and the existing
`conversation.spec.mjs` journey mounts it in the real app. The fixture
type-checks against freshly built declarations. As a negative control, a
misspelled interactions field fails `tsc`.

Run on a Linux Blox box on base `a34ba4f` (the local host-build guard
refused under load):
- `vitest run src/features/conversation
src/features/messages/MessageManagement.test.tsx
src/bundled/inbox/DraftsView.test.tsx`: 19 files, 221 tests passed
- `tsc --noEmit` and `biome check --error-on-warnings` on the touched
files: clean
- `pnpm author:build`, packed and installed into a copy of the consumer
fixture, then `pnpm build` (`tsc`): clean

No browser journeys were added or removed. The existing consumer journey
now mounts the scope; it runs only in hosted CI, not locally. Focus,
overlay and native-edit geometry are unchanged existing
`ConversationHost`/composer behavior that existing suites already cover.

## Limits and coordination

- Not exercised in the native desktop app or a browser journey. Hosted
CI runs the full suites.
- Two `ui.Conversation`s for the same channel each show that channel's
recovery notice, because recovery is per channel. The docs say to render
one per channel or card.
- No overlap in hunks or behavior with #2483 (Solo list arrangement/row
action in `service.tsx`), #1889, #2306 or #2303 (`contracts.ts`), #2083
(`MessageManagement.tsx`) or #2167 (`ConversationHost.tsx`). This PR
does not edit `contracts.ts`, `MessageManagement.tsx` or
`ConversationHost.tsx`.
- This PR doesn't adopt the scope in any plugin. That is separate work.

## Initiative context

[Buzz Threads
status](https://g2.sqprod.co/apps/kylez-buzz-threads-status)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Signed-off-by: Kyle Zemek <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

…y-untagged-reactions

* origin/main: (324 commits)
  fix(github): show private-repo body images from signed links (#3252)
  NEXUS-4029: Preserve semantic chips in the core composer (#2303)
  Make plugin signature enforcement opt-in (#2212)
  NEXUS-4156: Add workspace Leads and choose a chat's workspace (#2788)
  feat(plugins): report conclusively retired update providers (#3263)
  feat(messages): let attachment renderers open files from the host file card (#2239)
  feat(charts): bundle a Charts code-block renderer (#3226)
  Expose native reply grouping through Conversation.ui (#3245)
  NEXUS-4163: Keep plugin-owned chat deletion in Solo (#2787)
  NEXUS-4156: Expose Solo Workspaces to plugin regions (#2786)
  NEXUS-4022: Start region chats in the New Chat editor (#2784)
  feat(link-previews): unfurl web links below messages by default (#3225)
  fix(messages): keep names in literal Markdown as written when editing (#2834)
  feat(plugins): fetch a packaged managed plugin policy from a URL (#2504)
  fix(goose): enable deferred tool loading for goose agents (#3227)
  fix(unread): preserve manual intent in captured explicit reads (#3228)
  NEXUS-4337: Expose retained plugin update reviews (#3075)
  feat(conversation): add a link preview slot below messages (#3219)
  feat(plugins): let link previews read a public page's preview fields (#3217)
  Let sidebar row plugins decorate ordinary Solo chats (#3222)
  ...

* origin/main: (121 commits)
  Expose Solo region state before a component mounts (#3296)
  fix(builderlab): say a 401 was refused, not expired, and show each sign-in failure once (#3241)
  feat(agents): file new Solo chats in explicit personal workspaces (#2857)
  perf(css): limit broad style invalidation (#3267)
  Delay and fade in the Bestie badge celebration (#3292)
  fix(github): show private-repo body images from signed links (#3252)
  NEXUS-4029: Preserve semantic chips in the core composer (#2303)
  Make plugin signature enforcement opt-in (#2212)
  NEXUS-4156: Add workspace Leads and choose a chat's workspace (#2788)
  feat(plugins): report conclusively retired update providers (#3263)
  feat(messages): let attachment renderers open files from the host file card (#2239)
  feat(charts): bundle a Charts code-block renderer (#3226)
  Expose native reply grouping through Conversation.ui (#3245)
  NEXUS-4163: Keep plugin-owned chat deletion in Solo (#2787)
  NEXUS-4156: Expose Solo Workspaces to plugin regions (#2786)
  NEXUS-4022: Start region chats in the New Chat editor (#2784)
  feat(link-previews): unfurl web links below messages by default (#3225)
  fix(messages): keep names in literal Markdown as written when editing (#2834)
  feat(plugins): fetch a packaged managed plugin policy from a URL (#2504)
  fix(goose): enable deferred tool loading for goose agents (#3227)
  ...

Signed-off-by: Tyler Longwell <[email protected]>
Co-authored-by: Eva <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@buzz.block.builderlab.xyz>

* origin/main:
  NEXUS-4029: Offer folder chips in the composer (block#2789)
  perf(css): narrow effort button invalidation (block#3297)
  NEXUS-4433: Expose saved plugin installation source kind (block#3242)
  fix(identity): keep an unbacked key safe on Replace and unblock a corrupt saved key (block#3233)
  Expose Solo region state before a component mounts (block#3296)
  fix(builderlab): say a 401 was refused, not expired, and show each sign-in failure once (block#3241)
  feat(agents): file new Solo chats in explicit personal workspaces (block#2857)
  perf(css): limit broad style invalidation (block#3267)
  Delay and fade in the Bestie badge celebration (block#3292)
  fix(github): show private-repo body images from signed links (block#3252)
  NEXUS-4029: Preserve semantic chips in the core composer (block#2303)
  Make plugin signature enforcement opt-in (block#2212)
  NEXUS-4156: Add workspace Leads and choose a chat's workspace (block#2788)
  feat(plugins): report conclusively retired update providers (block#3263)
  feat(messages): let attachment renderers open files from the host file card (block#2239)
  feat(charts): bundle a Charts code-block renderer (block#3226)
  Expose native reply grouping through Conversation.ui (block#3245)

Signed-off-by: Joah Gerstenberg <[email protected]>

# Conflicts:
#	src/features/conversation/ComposerCompletions.test.tsx
#	src/features/conversation/ComposerCompletions.tsx
#	src/features/messages/MessageComposer.tsx