[recipes] repo-learning-coach: load .env via dotenv + fix research frontmatter

[eazene]

What & why

The repo-learning-coach recipe documents a .env workflow (Step 2: copy .env.example, fill in Supabase + OpenRouter credentials) but the app never loaded .env. Following the README as written, npm run sync and npm run dev both fail immediately:

Error: Missing required environment variable: SUPABASE_URL

There was no dotenv, no --env-file, and Node does not auto-load .env, so the server process (tsx server/index.ts) started with an empty environment.

Changes

• Add dotenv as a dependency and import 'dotenv/config' as the first import in the two server entry points (server/index.ts, server/sync-content.ts). Placed first so .env is loaded before server/supabase.ts reads process.env at module-init time. The client half (Vite) already loads .env on its own; this only affects the Node server process.
• Quote two research/*.md frontmatter summary: values that contained unquoted colons ("...the recipe: a local...", "...plain files: one config file..."). Unquoted colons are parsed as YAML mappings, which broke npm run sync with an "incomplete explicit mapping pair" error.

Testing

On a fresh .env (from .env.example) against an existing Open Brain Supabase project:

• npm run sync → Synced 3 lessons and 3 research documents.
• npm run dev → server GET /api/bootstrap returns HTTP 200 with the project + 3 lessons; Vite client returns HTTP 200.

No schema or app-logic changes; the core thoughts table is untouched.

🤖 Generated with Claude Code

[github-actions]

OB1 PR Gate

✅ Folder structure — All files are in allowed directories
✅ Required files — README.md and metadata.json found in all contribution folders
✅ Metadata valid — All metadata.json files passed JSON Schema validation
✅ No credentials — No API keys, tokens, or secrets detected
✅ SQL safety — No destructive SQL or core table modifications
✅ Category artifacts — Required file types present for each category
✅ PR format — Title follows [category] Description format
✅ No binary blobs — No oversized or binary files
✅ README completeness — All READMEs include Prerequisites, Steps, and Expected Outcome
✅ Contribution dependencies — All declared skill and primitive dependencies exist and are linked in README
✅ LLM clarity review — Covered by Claude PR Review workflow
✅ Remote MCP pattern — No local MCP server patterns detected — uses remote MCP correctly
✅ Tool audit link — Extensions/integrations link to the MCP Tool Audit guide
✅ Scope check — All changes are within the contribution folder(s)
✅ Internal links — All relative links in READMEs resolve to existing files

Result: All 15 checks passed! Ready for human review.

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Post-Merge Tasks

These don't block merge — they're reminders for admins after this PR lands.

• Add Repo Learning Coach to recipes/README.md
• Add Repo Learning Coach to root README.md community contributions section
• Post in OB1 Discord #show-and-tell