feat(echo-start): auto register template referral system

[Cyber-Mitch]

Description

• What: Auto-populate referral env vars when echo-start scaffolds from an external template by reading metadata files and writing referral codes into .env.local.
• Why: Ensures template creators receive referral credit automatically per issue Template referral system #612.
• How: Added helpers in packages/sdk/echo-start/src/index.ts to read .echo/template.json, echo-template.json, or
  package.json and upsert a framework-appropriate referral env var alongside the app ID.

Testing

• pnpm test:all ✅ (passes)
• pnpm --filter echo-start lint ✅ (package-specific lint passes; repo-wide lint still fails in packages/app/control, pre-existing)
• pnpm --filter echo-start type-check ✅ (package-specific type check passes; repo-wide type-check fails in packages/tests/provider-smoke, missing @types/node)
• Manual ✅ echo-start run with an external template confirms referral env var is added to .env.local

This closes #611

[vercel]

@Cyber-Mitch is attempting to deploy a commit to the Merit Systems Team on Vercel.

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[Cyber-Mitch]

@rsproule I'm done now

[Cyber-Mitch]

suggestion applied

[rsproule]

I think this .echo/template.json file is a cool strategy. But we do not currently have a mechanism to hit the echo control plane authenticated from inside echo-start.

Have you explored other designs / strategies here ? Like perhaps doing this registration directly in the echo control console instead of in echo start?

If we go forward with this .echo/template.json strategy, we need to think further around how this referrer actually registers.

[Cyber-Mitch]

@rsproule please review

[Cyber-Mitch]

Hello @rsproule you haven't reviewed yet

[rsproule]

Did you make any changes? I don't see answers to my questions in comments and this approach still does not actually do anything (doesn't register the referrer in echo)

[Cyber-Mitch]

Did you make any changes? I don't see answers to my questions in comments and this approach still does not actually do anything (doesn't register the referrer in echo)

I'll make the changes now

[Cyber-Mitch]

@rsproule Thanks for the feedback! I've updated the approach in this PR to address the issue of actually registering the referrer without needing authentication in echo-start. Instead of extracting a referral code and writing it to .env.local (which, as you noted, doesn't integrate with Echo's control plane), I've shifted to a link-based strategy:

• When an external template is used, we extract the GitHub repo owner (assuming it matches the Echo username/referrer).

• I then customize the app creation link in the app ID prompt to include a ?ref= query param (e.g., https://echo.merit.systems/new?ref=someuser). This guides the user to create the app via a referral link, which should register the referrer implicitly on Echo's side during signup/app creation.

• If the app ID is provided via CLI (for existing apps), we log a warning that referral can't be applied retroactively.

• Removed the old .env referral logic entirely, as it wasn't functional.

[Cyber-Mitch]

@rsproule Kindly review

[Cyber-Mitch]

@rsproule you haven't reviewed yet