fix(ai-proxy): use proper AI error classes instead of generic Error

[Scra3]

Summary

• ForestIntegrationClient.checkConnection() threw new Error(...) for unsupported integrations → now throws AIBadRequestError
• assertResponseOk() in Zendesk utils threw new Error(...) for API failures → now throws AIToolUnprocessableError
• Add CLAUDE.md to ai-proxy package with error handling guidelines

Without proper error classes, the agent's error middleware maps these to a generic 500 instead of the correct HTTP status code.

Test plan

• All 224 ai-proxy tests pass
• Lint passes

🤖 Generated with Claude Code

Note

Replace generic Error with typed AI error classes in ai-proxy

• ForestIntegrationClient.checkConnection now throws AIBadRequestError instead of a generic Error for unsupported integrations.
• zendesk/utils.assertResponseOk now throws AIToolUnprocessableError instead of a generic Error on non-OK responses.
• Adds a CLAUDE.md documenting the package's error handling policy: all thrown errors must extend AI error classes from src/errors.ts.

^{Macroscope summarized e5b5dd1.}

[qltysh]

Coverage Impact

This PR will not change total coverage.

Modified Files with Diff Coverage (2)

Rating	File	% Diff	Uncovered Line #s
	packages/ai-proxy/src/forest-integration-client.ts	100.0%
	packages/ai-proxy/src/integrations/zendesk/utils.ts	100.0%
	Total	100.0%

🚦 See full report on Qlty Cloud »

🛟 Help

• Diff Coverage: Coverage for added or modified lines of code (excludes deleted files). Learn more.

• Total Coverage: Coverage for the whole repository, calculated as the sum of all File Coverage. Learn more.

• File Coverage: Covered Lines divided by Covered Lines plus Missed Lines. (Excludes non-executable lines including blank lines and comments.)

  • Indirect Changes: Changes to File Coverage for files that were not modified in this PR. Learn more.