docs: clarify Terraform/CloudFormation deployment relationship

[drernie]

Summary

• Adds an introductory paragraph before the ### CloudFormation / ### Terraform split explaining that both paths use a CloudFormation stack, but Terraform additionally provisions foundational infrastructure (VPC, RDS, OpenSearch) first and wires it in automatically
• Removes the misleading mention of Terraform as just another way to drive CloudFormation under ### CloudFormation
• Fixes a broken blockquote in the Terraform section

Motivation

The existing docs implied Terraform was simply a CLI alternative for deploying a CloudFormation stack. In reality, the Terraform path is a two-layer architecture where Terraform owns the infrastructure and CloudFormation owns the application. Non-technical admins had no way to understand why a Terraform-deployed stack shows up in the CloudFormation console, or why they should not update it there directly.

Test plan

• Read the ## Installation Methods section as a non-technical admin
• Confirm ### CloudFormation and ### Terraform are now independent subsections with no cross-references
• Confirm docs render correctly on docs.quilt.bio

🤖 Generated with Claude Code

Greptile Summary

This PR improves the Installation.md documentation by clarifying the architectural relationship between the CloudFormation and Terraform deployment paths for Quilt. The changes address a common point of confusion for non-technical admins.

Key changes:

• Adds a new introductory paragraph explaining that both CloudFormation and Terraform deployment paths ultimately use a CloudFormation stack, but Terraform adds an outer layer that first provisions foundational infrastructure (VPC, RDS, OpenSearch) before wiring it into the CloudFormation stack.
• Includes practical guidance on when to use each deployment method.
• Removes the misleading mention of Terraform from the CloudFormation subsection, making clear that CloudFormation and Terraform are two independent paths.
• Fixes a broken blockquote in the Terraform section where the second line was missing its > prefix.

Confidence Score: 5/5

• Documentation-only change with no code impact; safe to merge.
• This is a purely documentation PR with three focused, accurate changes: an introductory paragraph that clarifies deployment architecture, removal of misleading cross-references, and a blockquote syntax fix. All changes align with the stated PR objectives and improve clarity for non-technical admins without introducing inaccuracies or breaking changes.
• No files require special attention.

Sequence Diagram

sequenceDiagram
    participant Admin
    participant Terraform
    participant CloudFormation
    participant AWS as AWS Resources

    Note over Admin,AWS: CloudFormation Path
    Admin->>CloudFormation: Deploy Quilt CFN template
    CloudFormation->>AWS: Provisions VPC, RDS, OpenSearch, App (single stack)
    AWS-->>Admin: Stack complete (CREATE_COMPLETE)

    Note over Admin,AWS: Terraform Path
    Admin->>Terraform: Apply Terraform modules
    Terraform->>AWS: Provisions VPC, RDS, OpenSearch (foundational infra)
    Terraform->>CloudFormation: Deploy Quilt CFN template (wired to infra)
    CloudFormation->>AWS: Provisions App layer (stack visible in console)
    AWS-->>Admin: Stack complete (CREATE_COMPLETE)

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_{Last reviewed commit: e684d00}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.32%. Comparing base (adae9cd) to head (4a865cd).

Additional details and impacted files

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  Coverage   44.32%   44.32%           
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  Files         813      813           
  Lines       32734    32734           
  Branches     5722     5722           
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  Hits        14509    14509           
  Misses      16221    16221           
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Flag	Coverage Δ
api-python	92.65% <ø> (ø)
catalog	19.52% <ø> (ø)
lambda	96.63% <ø> (ø)
py-shared	98.18% <ø> (ø)

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