bug: cycles, export, and embed commands crash with stack trace when no graph.db exists

[carlos-alm]

Found during dogfooding v2.2.3-dev.44e8146

Severity: Medium
Commands: codegraph cycles, codegraph export, codegraph embed

Reproduction

mkdir /tmp/test-no-graph && cd /tmp/test-no-graph && npm init -y
npm install @optave/codegraph@2.2.3-dev.44e8146
npx codegraph cycles    # crashes
npx codegraph export    # crashes
npx codegraph embed     # crashes

Expected behavior

All commands should show the same graceful error message as other commands:

No codegraph database found at <path>/.codegraph/graph.db.
Run "codegraph build" first to analyze your codebase.

Actual behavior

All three commands crash with an unhandled TypeError stack trace from better-sqlite3:

TypeError: Cannot open database because the directory does not exist
    at new Database (node_modules/better-sqlite3/lib/database.js:65:9)
    at Command.<anonymous> (src/cli.js:317:16)

Root cause

These three command handlers bypass the findDbPath() guard that most other commands use. They call new Database(dbPath) directly, which throws when the .codegraph/ directory doesn't exist.

Suggested fix

Add the same findDbPath() check or fs.existsSync() guard before opening the database in:

• cli.js cycles handler (~line 317)
• cli.js export handler (~line 278)
• embedder.js buildEmbeddings() (~line 327)