fix(slack): OAuth redirect handling

[bensabic]

Fixes Slack OAuth callback handling when the install flow depends on a specific redirect_uri.

The Slack adapter now accepts redirectUri as an explicit option on handleOAuthCallback(request, { redirectUri }), with backward-compatible fallback to redirect_uri on the callback URL when present. This fixes multi-redirect OAuth setups where Slack does not echo the redirect URI back as a query param.

Also includes:

• tests covering explicit redirectUri, precedence over query params, query-param fallback, and missing code
• README and Slack guide updates documenting the callback usage
• a patch changeset for @chat-adapter/slack

Validation:

• pnpm vitest run packages/adapter-slack/src/index.test.ts
• pnpm typecheck
• pnpm test

Closes #297

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Project	Deployment	Actions	Updated (UTC)
chat	Ready	Preview, Comment, Open in v0	Mar 27, 2026 3:19am
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