#12204: fix(discord): resolve numeric guildId/channelId pairs in channel allowlist

Fixes #12185 ## Summary When users configure Discord channel allowlists with numeric `guildId/channelId` pairs (e.g. `111222333/444555666`), `parseDiscordChannelInput` treated the channel part as a channel *name* rather than an ID. This caused the resolution to attempt a name-based lookup against guild channels, which always failed for numeric IDs, silently dropping inbound messages from those channels. ### Changes - **Numeric channel ID detection**: when both halves of `guild/channel` are all-digits, parse the channel part as `channelId` for direct API lookup - **Guild membership validation**: reject entries where the fetched channel belongs to a different guild than specified - **Graceful error handling**: catch 404/403 from channel lookups so one bad entry doesn't abort the entire batch - **Guild context preservation**: include `guildId` on unresolved results so downstream onboarding doesn't default to wildcard guild - **Name fallback**: when a numeric channel ID lookup fails and a guild was specified, fall back to name matching within that guild (supports channels with numeric names like "2024") ### Test plan - [x] `"111222333/444555666"` resolves via direct channel ID lookup (TDD — test written first) - [x] `"111222333/444555666"` where channel belongs to different guild → `resolved: false` with note - [x] `"111222333/999000111"` where channel ID is 404 → marks unresolved, doesn't abort batch, preserves `guildId` - [x] `"111222333/777888999"` where channel ID is 403 → marks unresolved, doesn't abort batch - [x] `"111222333/2024"` where "2024" is a channel name → falls back to name matching within guild - [x] All 7 new tests fail before fix, pass after - [x] All 12 existing discord test files pass (40+ tests) - [x] `pnpm build && pnpm check` clean <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates Discord allowlist parsing/resolution to correctly handle numeric `guildId/channelId` inputs by treating the channel segment as an ID (with optional guild-scoped name fallback on 404), adds a guild-membership consistency check for resolved channels, and improves channel fetch error classification (403 vs 404 vs invalid payload) so a single bad entry doesn’t abort batch resolution. The main logic lives in `src/discord/resolve-channels.ts`, where `parseDiscordChannelInput` now returns `{guildId, channelId}` when both segments are all-digits, and `fetchChannel` now returns a discriminated `FetchChannelResult` to avoid conflating forbidden/not-found/invalid responses. `src/discord/resolve-channels.test.ts` adds coverage for the numeric-pair path, guild mismatch rejection, 404/403 behavior, and malformed payload handling. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The changes are localized to Discord allowlist parsing/resolution, add targeted tests for the new numeric `guildId/channelId` path, and the new error classification avoids previously reported incorrect fallbacks. I did not find any additional deterministic logic issues in the diff beyond previously addressed threads. - No files require special attention <!-- greptile_other_comments_section --> <!-- /greptile_comment -->