fix(typescript): reject subpackage method collisions

[dimitropoulos]

Fern generates invalid TypeScript (that can't typecheck) when an endpoint/subpackage client name collisions occurs.

Repro: https://github.com/dimitropoulos/scratchpad/tree/fern-nested-group-method-collision
CI (TS2300 at both c declarations): https://github.com/dimitropoulos/scratchpad/actions/runs/33697294169

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[nitpickybot]

AI Review Summary

Adds a collision check between endpoint method names and subpackage client property names in the TS SDK generator. The logic is reasonable, but the hasWebSocketInTree cast smells, and throwing a bare Error deep in a constructor may produce a poor generator error experience. Also worth verifying that the check mirrors the actual naming/skip logic used at generation time (e.g. exported/inlined subpackages, hasEndpointsInTree semantics).

• 🟡 1 warning(s)
• 🔵 2 suggestion(s)

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[Copilot]

🟡 Changes recommended

The collision check currently ignores other generated public client members (e.g. root fetch() and websocket connect), so it can still emit invalid TypeScript for certain subpackage names.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR updates the TypeScript SDK client-class generator to proactively reject name collisions between generated endpoint methods and generated subpackage client accessors, preventing invalid TypeScript output (e.g. duplicate member declarations).

Changes:

• Add a constructor-time validation that detects endpoint-method vs subpackage-client name collisions and throws early.
• Add unit test coverage for the collision scenario.
• Add an unreleased generator changelog entry documenting the fix.

File summaries

File	Description
generators/typescript/sdk/client-class-generator/src/GeneratedSdkClientClassImpl.ts	Adds early validation for endpoint/subpackage client naming collisions during client generation.
generators/typescript/sdk/client-class-generator/src/test/GeneratedSdkClientClassImpl.test.ts	Adds a regression test asserting collisions are rejected with a helpful error.
generators/typescript/sdk/changes/unreleased/reject-subpackage-method-collisions.yml	Records the fix in the generator’s unreleased changelog.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 2
• Review effort level: Lite

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