Discord: fix /codex_resume identity resolution in brand-new threads

[huntharo]

Summary

Fixes /cas_resume failing on the first attempt in brand-new Discord threads by correcting the identity resolution in toConversationTargetFromCommand().

Why this matters

From #30: in a brand-new Discord thread, sending a first message before the agent has replied causes /cas_resume to show a generic "No active Codex sessions found" reply, with the picker only appearing ~40 seconds later via a retry.

Root cause: the slash interaction placed the slash user identity (e.g. slash:user-id) in ctx.from, with the real channel target in ctx.to. The expression ctx.from ?? ctx.to evaluated to "slash:user-id" (truthy string). normalizeDiscordConversationId() maps any slash: prefix to undefined, so toConversationTargetFromCommand() returned null — and the command could not resolve a conversation target for the picker.

Changes

src/controller.ts, toConversationTargetFromCommand() (line ~274): when ctx.from starts with "slash:", use ctx.to as the channel source instead of ctx.from. Established-channel behavior is unchanged — when ctx.from holds a discord:channel: or channel: identity, it continues to take precedence.

-    const conversationId = normalizeDiscordConversationId(ctx.from ?? ctx.to);
+    const sourceId = ctx.from?.startsWith("slash:") ? ctx.to : (ctx.from ?? ctx.to);
+    const conversationId = normalizeDiscordConversationId(sourceId);

Testing

Added a regression test in src/controller.test.ts with ctx.from = "slash:user-1" and ctx.to = "discord:channel:chan-1" — asserts the thread picker is sent to the correct channel identity ("channel:chan-1"), not a null target.

All 122 tests pass (pnpm typecheck + pnpm test).

Fixes #30

This contribution was developed with AI assistance (Claude Code).

[mvanhorn]

Summary

Traced through the fix and the regression test. The slash: prefix check correctly falls through to ctx.to for channel resolution, and the existing if (!conversationId) return null guard covers the case where ctx.to is also missing. Established-channel paths are untouched.

Recommendation

Looks good to merge.

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Review assisted by Claude Code