fix(channels): Include unjoined public channels in public-channel allowlist

[engfragui]

Overview

getPublicChannelIds built its allowlist from getChannels alone, which is membership-scoped and excludes public channels the user hasn't joined. This wrongly rejected threads in unjoined-but-public channels as private via assertChannelIsPublic, and left a latent masking bug in filterVisibleSearchResults.

Merge getChannels with workspaces.getPublicChannels and dedupe by id, mirroring the #249 fix in resolveChannelRef.

Reference

• Fixes getPublicChannelIds is membership-scoped — same bug #249 fixed in refs.ts #263
• Similar to fix(refs): resolve unjoined-but-public channels by name #249

Test Plan

• npm run build
• Via the UI, visit an unjoined channel (i.e. I picked "z.Cooking" but you do you)
• Copy the link of any thread inside that unjoined channel
• Extract the threadId from the URL (it's the last id in the URL)
• node dist/index.js thread view id:<threadId>
• Verify that the thread renders normally (instead of NOT_FOUND: This thread belongs to a private channel)

[engfragui]

@doistbot /review

[doistbot]

Thanks for putting together this fix for unjoined public channels, Francesca 😎 👊.

Few things worth tightening:

• The getChannels API call is likely redundant and can be removed, as getPublicChannels already returns all public channels regardless of membership (unless you specifically need to capture archived joined channels).

I also included a few optional follow-up notes in the details below.

Optional follow-up note (1)

• [P3] src/lib/public-channels.ts:17: This is now the third place that reimplements the "joined channels + getPublicChannels + dedupe by id" rule (alongside resolveChannelRef and listChannels). Since this PR exists because those call sites drifted apart, it would be better to extract a shared helper for this workspace-channel visibility logic and build the ID set from that, so future fixes only need to land once.

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[doist-release-bot]

🎉 This PR is included in version 2.45.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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