fix(desktop): resolve mentions from channel members [issue:#3204]

[tcballard]

Summary

Implements issue #3204 as the next separate contribution in the #3863 handoff workstream.

The mention picker was applying a local-managed-agent gate to every agent candidate, including agents already present in the current channel. That made a remote or otherwise non-local channel member impossible to mention, while unrelated local persona rows could appear instead.

Scope

Included

• Removes the local-managed-agent requirement from channel-member mention candidates.
• Keeps the existing invocability and archived-identity checks for non-member agent candidates.
• Preserves channel membership on the candidate, so a channel-member agent is not labeled “not in channel” and can be selected with the correct pubkey.
• Adds a focused E2E regression covering a profile-backed agent that is a member of #general but is not locally managed.

Excluded

• No new relay/API or Nostr event kind.
• No change to agent deployment or persona-minting behavior ([Bug] Deploy team to channel force-mints new agent keypair per persona (bypasses reuse) #3639 remains separate).
• No change to the DM recipient picker.
• No command-palette/autocomplete redesign beyond correcting this existing mention candidate source.
• No OEXL-specific code, matching, outcome contracts, payments, ledger state, or settlement semantics.

Product / Architecture Decisions

• Channel membership remains the authoritative source for candidates already in the open channel.
• Local managed agents and explicitly invocable relay agents retain their existing non-member behavior.
• Existing duplicate-name disambiguation, profile labels, archived filtering, and p-tag extraction are reused unchanged.

User-Facing Contract

In a channel composer, @ now offers agent identities that are current members of that channel even when their runtime is hosted on another machine or is not represented in this Desktop’s local managed-agent list. Those rows are shown as channel members rather than “not in channel.” Non-member, non-invocable agent rows remain hidden.

Verification

Ran

• Focused Biome check on useMentions.ts and mentions.spec.ts
• node --import ./test-loader.mjs --experimental-strip-types --test src/features/agents/lib/agentAutocompleteEligibility.test.mjs (18 passed)
• git diff --check

Added

• desktop/tests/e2e/mentions.spec.ts: channel-member, non-local agent is visible and not labeled “not in channel.”

The full Playwright browser run and TypeScript build were attempted but could not complete in this environment because the temporary checkout’s Vite/Node dependency loader stalled while reading vite.config.ts; this is an environment/toolchain limitation, not a test assertion failure.

UI Evidence

This changes autocomplete behavior, not layout or styling. A screenshot/recording could not be captured because the local browser build was blocked by the dependency-loader issue described above; the regression is represented in the focused E2E spec for maintainers to run in CI.

Review Path

1. desktop/src/features/messages/lib/useMentions.ts
2. desktop/tests/e2e/mentions.spec.ts

Notes For Reviewer

This is an independent branch and PR, not stacked on the workflow-history or Canvas-history contributions. It deliberately does not address the adjacent persona duplication, DM recipient, or command-palette workstreams.

[Chessing234]

nice narrow fix. worth a regression case where the channel member is respond_to:allowlist but the viewer is not on the list — autocomplete should still hide them.

[tcballard]

@Chessing234 Added this in ba6650a. The regression seeds mira as a #general channel member with respond_to: allowlist, leaves the mock viewer off the allowlist, and asserts that @mi autocomplete stays hidden. The focused Playwright test passes (1 passed).