fix(slack): allow installation before organization setup

[TheodoreSpeaks]

Summary

• Let installs initiated from Slack finish without a Sim session or organization, then show setup guidance with links to Slack and Sim.
• Connect the app to an organization later through the existing admin setup. Preserve state-bound OAuth checks and store no credentials for standalone installs.
• No database changes.

Type of Change

• Bug fix

Testing

78 focused tests passed across six suites, covering callback validation, session isolation, OAuth exchange, setup guidance rendering, and existing setup. Repository lint, all 46 audits, generated-artifact checks, and the block registry check passed. Typechecking runs in CI; the live installation flow has not been retested with this change.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 17, 2026 12:01am UTC

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the previously reported wording and styling concerns are resolved, and no new actionable issue was identified.

Summary

This PR enables Slack-initiated installation without requiring a Sim session or organization while preserving the existing authenticated, state-bound organization setup flow.

• Exchanges and validates standalone Slack OAuth grants without retaining credentials or binding an organization.
• Redirects standalone installs to a public setup-guidance page.
• Keeps organization-initiated callbacks on the authenticated setup path.
• Adds callback, OAuth validation, rendering, and session-isolation coverage.
• Updates Slack setup documentation.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Slack OAuth callback] --> B{Nonempty state?}
  B -->|Yes| C[Require Sim session]
  C --> D[Validate state and complete organization setup]
  D --> E[Redirect to organization Slack settings]
  B -->|No| F[Exchange one-time Slack code]
  F --> G[Validate app, scopes, and workspace]
  G --> H[Discard grant credentials]
  H --> I[Redirect to public setup-guidance page]

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[TheodoreSpeaks]

@greptile

[TheodoreSpeaks]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

@TheodoreSpeaks I have started the AI code review. It will take a few minutes to complete.

[cubic-dev-ai]

No issues found across 11 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}