fix(pods): preserve equals signs in --env values

[crazywriter1]

Summary

• Parse prime pods create --env KEY=VALUE with split("=", 1), matching sandbox CLI behavior
• Reject malformed env entries that lack =
• Add regression tests for values containing = (e.g. connection strings)

Test plan

• uv run pytest packages/prime/tests/test_pods_create.py -q

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Note

Low Risk
Small CLI input-validation change with tests; no auth or API contract changes beyond correct env var payloads.

Overview
Fixes prime pods create --env parsing so variable values keep any = characters (e.g. Postgres URLs with query params, FLAGS=a=b=c), aligning with the sandbox CLI.

Parsing now splits only on the first =, rejects entries without =, and exits early with a KEY=VALUE error before availability is loaded. Regression tests cover multi-= values and invalid --env input.

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