feat(channel): add Slack channel configuration UI

[tcp404]

Description

Add a Slack channel configuration UI to the Settings → Channels panel, moving Slack from the coming_soon placeholder to an active channel with a full config form.

• SlackConfigForm.tsx (new, modeled on TelegramConfigForm): two-token input — Bot Token (xoxb-) and App-Level Token (xapp-), both Input.Password with visibility toggle and soft prefix validation. "Test" validates only the Bot Token via auth.test; on success it auto-enables the plugin submitting both tokens. Includes the pairing-request flow, authorized-users list, and a Next-Steps guide.
• ChannelModalContent.tsx (wiring): adds 'slack' to the platform type; introduces slackPluginStatus / useChannelModelSelection('slack') / slackTokenRef / slackEnableLoading / handleToggleSlackPlugin; removes Slack from comingSoonChannels and inserts an active slackChannel card (right after Telegram); hooks up toggle dispatch, pluginStatusChanged, and loadPluginStatus. Discord stays coming_soon.
• i18n: adds settings.assistant.slack* keys (18) plus settings.assistant.unknownUser across all 13 locales (real translations, not placeholders); regenerates i18n-keys.d.ts.
• PRD: docs/prds/remote/channels/channels.md — Slack moved coming_soon → active, new F-WEBUI-13b section.

Wire contract (agreed with backend)

• Plugin id is the bare slack.
• testPlugin sends { plugin_id: 'slack', token: <xoxb> } (validates Bot Token only).
• enablePlugin sends { plugin_id: 'slack', config: { credentials: { token: <xoxb>, app_token: <xapp> } } } — key name is exactly app_token (underscore).
• All wiring reuses the generic channel.* IPC; no new IPC entry points. Pairing / authorized users are filtered by platformType === 'slack'.

Related Issues

• Closes #

Type of Change

• feat — New feature (non-breaking change which adds functionality)

Atomic PR Checklist (Rule 1)

• This PR contains exactly one feature or bug fix that cannot be further decomposed
• The PR title follows Conventional Commit format: <type>(<scope>): <subject> (English)

Local Checks (Rule 3)

• bun run format — formatting passes
• bun run lint — no lint errors (pre-existing repo warnings only; just push lint-strict gate passed)
• bunx tsc --noEmit — no type errors (0 errors)
• bunx vitest run — tests pass (3964 passed / 5 skipped via just push)
• i18n validated (bun run i18n:types + node scripts/check-i18n.js)
• New/changed user-facing text uses i18n keys (no hardcoded strings)

Runtime Verification

• Verified on macOS
• Verified on Windows
• Verified on Linux
• I have performed a self-review of my own code

Additional Context

• The companion backend PR lives in the aioncore repo on branch boii/feat/channel-slack.
• This change lands in aionui (open-source edition); it will be synced to aionpro afterwards.
• No live end-to-end verification yet — validated via static gates (format / lint / tsc --noEmit / vitest / i18n check) + code review + front/back contract cross-check. Runtime verification is deferred to a shared integration instance.
• The repo-wide hardcoded 'Unknown User' in other channel forms (Telegram/Lark/DingTalk/WeChat/WeCom) is pre-existing debt and intentionally out of scope here; this PR only introduces i18n for its own new file (ratchet, no regression).

[codecov]

Codecov Report

❌ Patch coverage is 0% with 223 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ettingsModal/contents/channels/SlackConfigForm.tsx	0.00%	194 Missing ⚠️
...ngsModal/contents/channels/ChannelModalContent.tsx	0.00%	29 Missing ⚠️

📢 Thoughts on this report? Let us know!