test: add sample market data fixture

[mehmetyavuzz43]

Adds a JSON fixture representing a sample market with realistic fields, to be used in unit tests or examples.

---

Note

Introduces a simple tooling and test fixture addition.

• Adds scripts/bash/check_env.sh to validate .env presence and required vars (POLYGON_WALLET_PRIVATE_KEY, OPENAI_API_KEY); exits with error if missing/empty
• Adds tests/fixtures/sample_market.json providing realistic market data for unit tests/examples

^{Written by Cursor Bugbot for commit 07840b6. This will update automatically on new commits. Configure here.}

[cursor]

Last line of .env skipped without trailing newline

The while IFS='=' read -r key value loop fails to process the last line of the .env file if it doesn't end with a trailing newline. When read encounters EOF without a newline, it returns a non-zero exit status even though it successfully populated the variables, causing the while loop to exit before processing that line. This could silently skip exporting critical environment variables like OPENAI_API_KEY, leading the validation to incorrectly report them as missing. The fix requires adding || [ -n "$key" ] to the while condition.