feat: add responses passthrough

[Lumysia]

No description provided.

[Copilot]

Pull request overview

Adds an OpenAI-style responses passthrough to the Copilot proxy so clients can call /responses (and /v1/responses) and receive the upstream Copilot response (including streaming metadata) largely unchanged.

Changes:

• Introduces a new Copilot service (createResponses) that POSTs to Copilot’s /responses endpoint and returns the upstream Response.
• Adds Hono routing for /responses and registers it under both /responses and /v1/responses.
• Adds tests covering basic POST behavior and preservation of streaming headers/body; updates README endpoint documentation.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/create-responses.test.ts	Adds unit tests for the new responses passthrough behavior (JSON + streaming).
src/services/copilot/create-responses.ts	Implements the Copilot /responses service call and error handling.
src/routes/responses/route.ts	Adds a new route that forwards request JSON to Copilot and streams back status/headers/body.
src/server.ts	Registers the new responses routes under both unversioned and /v1 paths.
README.md	Documents the new endpoints and simplifies the README structure.
bun.lock	Lockfile metadata update (configVersion).

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[Copilot]

/// <reference lib="dom" /> is the only triple-slash lib reference in the repo. Since the project’s TypeScript configuration controls global libs, it’s better to avoid per-file lib references here (they can create inconsistent typing/duplicate lib definitions across files). Consider removing this and, if DOM types are actually needed project-wide, add them in tsconfig.json (or rely on @types/bun) instead.

Suggested change

/// <reference lib="dom" />

[Copilot]

The error message "Failed to create response" is a bit ambiguous/inconsistent with the endpoint name (/responses) and other service errors in this repo (e.g., "Failed to create embeddings", "Failed to create chat completions"). Consider renaming it to clearly identify the failing operation (e.g., "Failed to create responses") so logs and client errors are easier to interpret.

Suggested change

	if (!response.ok) throw new HTTPError("Failed to create response", response)
	if (!response.ok) throw new HTTPError("Failed to create responses", response)

[Copilot]

The new Markdown tables in this section start with a double pipe (|| ...). In standard Markdown this creates an extra empty first column, which makes the table render with a blank leading column. Use a single leading pipe (| ...) for the header and separator rows to avoid the extra column.

[Copilot]

This table also starts with ||, which renders an extra blank first column in Markdown. Use a single leading | on the header/separator rows instead.

[Copilot]

Same Markdown table formatting issue here: the rows start with ||, which adds an unintended empty first column when rendered. Prefer a single leading | for these rows.