fix(stubs): implement openai http_delete + make NoopIntentExtractor a true no-op

[KooshaPari]

Summary

• forge_repo: MockHttpClient.http_delete (inside #[cfg(test)]) now calls self.client.delete(url).send().await? instead of unimplemented!()
• forge_domain: NoopIntentExtractor returns Ok(ExtractedIntent { .. Null .. }) from extract_intent and Ok(false) from verify_extraction — true no-ops instead of propagating errors

Verification

• git grep -n "unimplemented!()" -- 'crates/**/*.rs' | grep -v test | grep -v mock — neither touched file appears
• cargo check -p forge_repo -p forge_domain exit 0
• cargo clippy -p forge_repo -p forge_domain -- -D warnings exit 0

🤖 Generated with Claude Code

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❌ Phenotype Agent
❌ Dmouse92
❌ KooshaPari

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