Include generated docs in local circuit prompt

[Fire-Fairy84]

Proposed Changes

• Load the generated tscircuit docs from https://docs.tscircuit.com/ai.txt when building the local circuit prompt.
• Include the generated docs ahead of the existing handwritten API overview when available.
• Cache the generated-docs fetch during the process and keep prompt creation resilient if the optional docs endpoint is unavailable.
• Add focused mocked-fetch coverage for the inclusion and fallback paths.
• Skip OpenAI-backed tests when OPENAI_API_KEY is not set, so the default CI test run remains deterministic.

Proof

npx tsc --noEmit
npx biome check lib/prompt-templates/create-local-circuit-prompt.ts tests/prompt-templates/create-local-circuit-prompt.test.ts tests/utils/generate-random-prompts.test.ts
npx bun test --timeout 50000
npm run build

All commands passed locally.

/claim #45

[Fire-Fairy84]

CI is green now after the follow-up fix:

• Type Check: passing
• Bun Test: passing